Allow RVFI to be unset

This change enables one to leave RVFI unset. When this is done,
ibexc_top_tracing is equivilant to ibexc_top, which is useful when using
the same module hierachy for both simulation and synthesis.

ibex_top_tracing.core

@@ -18,7 +18,6 @@ parameters:
   RVFI:
     datatype: bool
     paramtype: vlogdefine
-    default: true
 
   SYNTHESIS:
     datatype: bool
@@ -111,8 +110,6 @@ targets:
   default: &default_target
     filesets:
       - files_rtl
-    parameters:
-      - RVFI=true
     toplevel: ibex_top_tracing
 
   lint:

rtl/ibexc_top_tracing.sv

@@ -94,7 +94,7 @@ module ibex_top_tracing import ibex_pkg::*; import cheri_pkg::*; #(
   output logic                         alert_major_bus_o
 );
 
-
+`ifdef RVFI
   logic        rvfi_valid;
   logic [63:0] rvfi_order;
   logic [31:0] rvfi_insn;
@@ -140,6 +140,7 @@ module ibex_top_tracing import ibex_pkg::*; import cheri_pkg::*; #(
   assign unused_rvfi_ext_nmi = rvfi_ext_nmi;
   assign unused_rvfi_ext_debug_req = rvfi_ext_debug_req;
   assign unused_rvfi_ext_mcycle = rvfi_ext_mcycle;
+`endif
 
   ibexc_top #(
     .DmHaltAddr       (DmHaltAddr       ),
@@ -263,10 +264,6 @@ module ibex_top_tracing import ibex_pkg::*; import cheri_pkg::*; #(
 
 // ibex_tracer relies on the signals from the RISC-V Formal Interface
 // synthesis translate_off
-`ifndef RVFI
-   $fatal("Fatal error: RVFI needs to be defined globally.");
-`endif
-
 `ifdef RVFI
   ibex_tracer #(
     .DataWidth        (DataWidth)