[topgen] Don't generate empty clock_reset_export entries

The check_clk_rst_export function was essentially the same thing as
setdefault(). Since topgen's merge.py is actually the only thing that
reads this key, keep the same defaulting behaviour but don't actually
generate extra entries.

If we don't do this, we have to add clock_reset_export to the optional
fields list for every type in topgen/validate.py to avoid a warning.

Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>
diff --git a/hw/top_earlgrey/data/autogen/top_earlgrey.gen.hjson b/hw/top_earlgrey/data/autogen/top_earlgrey.gen.hjson
index 58b5362..49679ca 100644
--- a/hw/top_earlgrey/data/autogen/top_earlgrey.gen.hjson
+++ b/hw/top_earlgrey/data/autogen/top_earlgrey.gen.hjson
@@ -413,7 +413,6 @@
         rst_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x40000000
-      clock_reset_export: []
       clock_group: secure
       clock_connections:
       {
@@ -573,7 +572,6 @@
         rst_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x40010000
-      clock_reset_export: []
       clock_group: secure
       clock_connections:
       {
@@ -733,7 +731,6 @@
         rst_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x40020000
-      clock_reset_export: []
       clock_group: secure
       clock_connections:
       {
@@ -893,7 +890,6 @@
         rst_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x40030000
-      clock_reset_export: []
       clock_group: secure
       clock_connections:
       {
@@ -1054,7 +1050,6 @@
         rst_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x40040000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_peri
@@ -1123,7 +1118,6 @@
         rst_ni: rstmgr_resets.rst_spi_device_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x40050000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_peri
@@ -1269,7 +1263,6 @@
         rst_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x40100000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_timers
@@ -1497,7 +1490,6 @@
         rst_edn_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x40130000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_timers
@@ -1830,7 +1822,6 @@
         rst_ni: rstmgr_resets.rst_lc_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x40140000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_timers
@@ -2296,7 +2287,6 @@
         AccuCntDw: 16
         LfsrSeed: 0x7FFFFFFF
       }
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_timers
@@ -2468,7 +2458,6 @@
         rst_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x40160000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_timers
@@ -2594,7 +2583,6 @@
       domain: Aon
       base_addr: 0x40400000
       generated: "true"
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_powerup
@@ -2799,7 +2787,6 @@
       domain: Aon
       base_addr: 0x40410000
       generated: "true"
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_powerup
@@ -2945,7 +2932,6 @@
       domain: Aon
       base_addr: 0x40420000
       generated: "true"
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_powerup
@@ -3120,7 +3106,6 @@
       domain: Aon
       base_addr: 0x40460000
       generated: "true"
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_secure
@@ -3300,7 +3285,6 @@
       domain: Aon
       base_addr: 0x40470000
       generated: "true"
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_secure
@@ -3754,7 +3738,6 @@
       }
       domain: Aon
       base_addr: 0x40510000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_peri
@@ -3882,7 +3865,6 @@
       }
       base_addr: 0x41000000
       generated: "true"
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_infra
@@ -4233,7 +4215,6 @@
       }
       base_addr: 0x41010000
       generated: "true"
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_secure
@@ -4281,7 +4262,6 @@
         rst_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x41100000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_aes
@@ -4494,7 +4474,6 @@
         rst_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x41110000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_hmac
@@ -4594,7 +4573,6 @@
         rst_edn_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x41120000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_kmac
@@ -4766,7 +4744,6 @@
         rst_edn_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x41130000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_secure
@@ -5125,7 +5102,6 @@
         rst_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x41150000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_secure
@@ -5280,7 +5256,6 @@
         rst_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x41160000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_secure
@@ -5421,7 +5396,6 @@
         rst_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x41170000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_secure
@@ -5526,7 +5500,6 @@
         rst_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x41180000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_secure
@@ -5633,7 +5606,6 @@
         rst_otp_ni: rstmgr_resets.rst_lc_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x411C0000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_secure
@@ -5759,7 +5731,6 @@
         rst_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
       }
       base_addr: 0x411D0000
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_otbn
@@ -5894,7 +5865,6 @@
           index: -1
         }
       ]
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_infra
@@ -5943,7 +5913,6 @@
           index: -1
         }
       ]
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_infra
@@ -5993,7 +5962,6 @@
           index: -1
         }
       ]
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_io_div4_infra
@@ -6120,7 +6088,6 @@
           index: -1
         }
       ]
-      clock_reset_export: []
       clock_connections:
       {
         clk_i: clkmgr_clocks.clk_main_infra
@@ -6543,7 +6510,6 @@
         rst_main_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
         rst_fixed_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
-      clock_reset_export: []
       clock_connections:
       {
         clk_main_i: clkmgr_clocks.clk_main_infra
@@ -7265,7 +7231,6 @@
       {
         rst_peri_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
       }
-      clock_reset_export: []
       clock_connections:
       {
         clk_peri_i: clkmgr_clocks.clk_io_div4_infra
diff --git a/hw/top_earlgrey/ip/xbar_main/data/autogen/xbar_main.gen.hjson b/hw/top_earlgrey/ip/xbar_main/data/autogen/xbar_main.gen.hjson
index af5679a..4222728 100644
--- a/hw/top_earlgrey/ip/xbar_main/data/autogen/xbar_main.gen.hjson
+++ b/hw/top_earlgrey/ip/xbar_main/data/autogen/xbar_main.gen.hjson
@@ -20,7 +20,6 @@
     rst_main_ni: rstmgr_resets.rst_sys_n[rstmgr_pkg::Domain0Sel]
     rst_fixed_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
   }
-  clock_reset_export: []
   clock_connections:
   {
     clk_main_i: clkmgr_clocks.clk_main_infra
diff --git a/hw/top_earlgrey/ip/xbar_peri/data/autogen/xbar_peri.gen.hjson b/hw/top_earlgrey/ip/xbar_peri/data/autogen/xbar_peri.gen.hjson
index e8dceae..4fabea0 100644
--- a/hw/top_earlgrey/ip/xbar_peri/data/autogen/xbar_peri.gen.hjson
+++ b/hw/top_earlgrey/ip/xbar_peri/data/autogen/xbar_peri.gen.hjson
@@ -18,7 +18,6 @@
   {
     rst_peri_ni: rstmgr_resets.rst_sys_io_div4_n[rstmgr_pkg::Domain0Sel]
   }
-  clock_reset_export: []
   clock_connections:
   {
     clk_peri_i: clkmgr_clocks.clk_io_div4_infra
diff --git a/util/topgen/merge.py b/util/topgen/merge.py
index 9d6688f..9f0553c 100644
--- a/util/topgen/merge.py
+++ b/util/topgen/merge.py
@@ -546,15 +546,6 @@
     return result
 
 
-# Check if the export field already exists
-# If yes, return it
-# If no, set a default and return that
-def check_clk_rst_export(module):
-    if 'clock_reset_export' not in module:
-        module['clock_reset_export'] = []
-    return module['clock_reset_export']
-
-
 def amend_clocks(top: OrderedDict):
     """Add a list of clocks to each clock group
        Amend the clock connections of each entry to reflect the actual gated clock
@@ -587,7 +578,7 @@
         clock_connections = OrderedDict()
 
         # Ensure each module has a default case
-        export_if = check_clk_rst_export(ep)
+        export_if = ep.get('clock_reset_export', [])
 
         # if no clock group assigned, default is unique
         ep['clock_group'] = 'secure' if 'clock_group' not in ep else ep[
@@ -682,7 +673,7 @@
 
         # This code is here to ensure if amend_clocks/resets switched order
         # everything would still work
-        export_if = check_clk_rst_export(module)
+        export_if = module.get('clock_reset_export', [])
 
         # There may be multiple export interfaces
         for intf in export_if: