[reggen] Add Parameter list to the hjson format

- add `param_list` in IP configuration
- The parameter name can be used in `multireg["count"]` field
- `param_list` is added to the register package

This is related to #30 #47
diff --git a/util/reggen/gen_rtl.py b/util/reggen/gen_rtl.py
index 9e2ce58..8d1933c 100644
--- a/util/reggen/gen_rtl.py
+++ b/util/reggen/gen_rtl.py
@@ -89,6 +89,7 @@
     regs = []
     wins = []
     blocks = []
+    params = []
 
     def __init__(self):
         self.width = 32
@@ -98,6 +99,7 @@
         self.regs = []
         self.wins = []
         self.blocks = []
+        self.params = []
 
 
 def escape_name(name):
@@ -208,6 +210,8 @@
 
     log.info("Data Width is set to %d bits", block.width)
 
+    block.params = obj["param_list"] if "param_list" in obj else []
+
     for r in obj["registers"]:
         # Check if any exception condition hit
         if 'reserved' in r: