[dv] Fix riscv_mem_error_test

Memory errors trigger the same exception as PMP failures. For this test
we simply need to return to the failing instructions rather than the
more complex handling from the PMP exception handler.

dv/uvm/core_ibex/riscv_dv_extension/ibex_asm_program_gen.sv

@@ -13,6 +13,7 @@ class ibex_asm_program_gen extends riscv_asm_program_gen;
 
   virtual function void gen_program();
     string instr[$];
+    bit disable_pmp_exception_handler = 0;
 
     default_include_csr_write = {
       MSCRATCH,
@@ -54,6 +55,11 @@ class ibex_asm_program_gen extends riscv_asm_program_gen;
 
     riscv_csr_instr::create_csr_filter(cfg);
 
+    if ($value$plusargs("disable_pmp_exception_handler", disable_pmp_exception_handler) &&
+        disable_pmp_exception_handler) begin
+      cfg.pmp_cfg.enable_pmp_exception_handler = 0;
+    end
+
     super.gen_program();
 
     // Override the main gen_program() routine to append our own custom test_done/test_fail routines

dv/uvm/core_ibex/riscv_dv_extension/testlist.yaml

@@ -585,6 +585,7 @@
     +randomize_csr=1
     +enable_unaligned_load_store=1
     +suppress_pmp_setup=1
+    +disable_pmp_exception_handler=1
   rtl_test: core_ibex_mem_error_test
   sim_opts: >
     +require_signature_addr=1