[dv] Verilator unused parameter handling

Forward a currently unused parameter.

Disable error exit for warnings. Newer Verilator versions will fail if
for example parameters are unused. As this test does not cover
everything, allow those warning to be printed, but not fail the build.

dv/cs_registers/tb/tb_cs_registers.sv

@@ -59,6 +59,7 @@ module tb_cs_registers #(
   /* verilator lint_off PINMISSING */
   ibex_cs_registers #(
     .DbgTriggerEn     (DbgTriggerEn),
+    .ICache           (ICache),
     .MHPMCounterNum   (MHPMCounterNum),
     .MHPMCounterWidth (MHPMCounterWidth),
     .PMPEnable        (PMPEnable),

dv/cs_registers/tb_cs_registers.core

@@ -124,3 +124,4 @@ targets:
           - '-CFLAGS "-std=c++14 -Wall -DTOPLEVEL_NAME=tb_cs_registers -DVM_TRACE_FMT_FST -g"'
           - '-LDFLAGS "-pthread -lutil -lelf"'
           - "-Wall"
+          - '-Wno-fatal' # Do not fail on (style) issues, only warn about them.