[rtl] Avoid name collision in ibex_pmp.sv

Recent versions of Verilator complain about the code that was there
because the csr_pmp_cfg argument clashes with a name in ibex_core.sv.

What's more, they mean different things! In ibex_core.sv, it was the
PMP configuration for the entire core. In the functions, it's the PMP
configuration for a single region. This patch adds a "region_" prefix
to the names, which fixes both the Verilator warning and my confusion!

rtl/ibex_pmp.sv

@@ -51,16 +51,16 @@ module ibex_pmp #(
   //                                                            \--> pmp_req_err_o
 
   // Compute permissions checks that apply when MSECCFG.MML is set. Added for Smepmp support.
-  function automatic logic mml_perm_check(ibex_pkg::pmp_cfg_t  csr_pmp_cfg,
+  function automatic logic mml_perm_check(ibex_pkg::pmp_cfg_t  region_csr_pmp_cfg,
                                           ibex_pkg::pmp_req_e  pmp_req_type,
                                           ibex_pkg::priv_lvl_e priv_mode,
                                           logic                permission_check);
     logic result = 1'b0;
-    logic unused_cfg = |csr_pmp_cfg.mode;
+    logic unused_cfg = |region_csr_pmp_cfg.mode;
 
-    if (!csr_pmp_cfg.read && csr_pmp_cfg.write) begin
+    if (!region_csr_pmp_cfg.read && region_csr_pmp_cfg.write) begin
       // Special-case shared regions where R = 0, W = 1
-      unique case ({csr_pmp_cfg.lock, csr_pmp_cfg.exec})
+      unique case ({region_csr_pmp_cfg.lock, region_csr_pmp_cfg.exec})
         // Read/write in M, read only in S/U
         2'b00: result =
             (pmp_req_type == PMP_ACC_READ) |
@@ -77,14 +77,15 @@ module ibex_pmp #(
         default: ;
       endcase
     end else begin
-      if (csr_pmp_cfg.read & csr_pmp_cfg.write & csr_pmp_cfg.exec & csr_pmp_cfg.lock) begin
+      if (region_csr_pmp_cfg.read & region_csr_pmp_cfg.write &
+          region_csr_pmp_cfg.exec & region_csr_pmp_cfg.lock) begin
         // Special-case shared read only region when R = 1, W = 1, X = 1, L = 1
         result = pmp_req_type == PMP_ACC_READ;
       end else begin
         // Otherwise use basic permission check. Permission is always denied if in S/U mode and
         // L is set or if in M mode and L is unset.
         result = permission_check &
-                 (priv_mode == PRIV_LVL_M ? csr_pmp_cfg.lock : ~csr_pmp_cfg.lock);
+                 (priv_mode == PRIV_LVL_M ? region_csr_pmp_cfg.lock : ~region_csr_pmp_cfg.lock);
       end
     end
     return result;
@@ -105,15 +106,15 @@ module ibex_pmp #(
 
   // A wrapper function in which it is decided which form of permission check function gets called
   function automatic logic perm_check_wrapper(logic                csr_pmp_mseccfg_mml,
-                                              ibex_pkg::pmp_cfg_t  csr_pmp_cfg,
+                                              ibex_pkg::pmp_cfg_t  region_csr_pmp_cfg,
                                               ibex_pkg::pmp_req_e  pmp_req_type,
                                               ibex_pkg::priv_lvl_e priv_mode,
                                               logic                permission_check);
-    return csr_pmp_mseccfg_mml ? mml_perm_check(csr_pmp_cfg,
+    return csr_pmp_mseccfg_mml ? mml_perm_check(region_csr_pmp_cfg,
                                                 pmp_req_type,
                                                 priv_mode,
                                                 permission_check) :
-                                 orig_perm_check(csr_pmp_cfg.lock,
+                                 orig_perm_check(region_csr_pmp_cfg.lock,
                                                  priv_mode,
                                                  permission_check);
   endfunction