Add the Width parameter to prim_buf module

The prim_buf.sv file in Ibex is a manual copy of a file which is
typically auto-generated by FuseSoC/primgen. However, Ibex DV doesn't
yet run FuseSoC, and we provide a pregenerated copy instead. The
auto-generated file and its copy got out of sync. Fix that by adding the
new Width parameter.

dv/uvm/core_ibex/common/prim/prim_buf.sv

@@ -8,13 +8,15 @@
 // Its contents are taken from the file which would be generated by FuseSoC.
 // https://github.com/lowRISC/ibex/issues/893
 
-module prim_buf (
-  input in_i,
-  output logic out_o
+module prim_buf #(
+  parameter int Width = 1
+) (
+  input        [Width-1:0] in_i,
+  output logic [Width-1:0] out_o
 );
 
   if (1) begin : gen_generic
-    prim_generic_buf u_impl_generic (
+    prim_generic_buf#(.Width(Width)) u_impl_generic (
       .*
     );
   end