[rstmgr] remove buffer usage

Signed-off-by: Timothy Chen <timothytim@google.com>
diff --git a/hw/ip/rstmgr/rtl/rstmgr_por.sv b/hw/ip/rstmgr/rtl/rstmgr_por.sv
index 282413a..74aed24 100644
--- a/hw/ip/rstmgr/rtl/rstmgr_por.sv
+++ b/hw/ip/rstmgr/rtl/rstmgr_por.sv
@@ -49,7 +49,9 @@
   // The stable is a vote of all filter stages.
   // Only when all the stages agree is the reset considered stable and count allowed.
 
-  prim_clock_mux2 u_rst_clean_mux (
+  prim_clock_mux2 #(
+    .NoFpgaBufG(1'b1)
+  ) u_rst_clean_mux (
     .clk0_i(rst_filter_n[FilterStages-1]),
     .clk1_i(scan_rst_ni),
     .sel_i(scanmode_i),