pointer masking: Support _smnpm to --isa

disasm/isa_parser.cc

@@ -320,6 +320,8 @@ isa_parser_t::isa_parser_t(const char* str, const char *priv)
       extension_table[EXT_ZICFISS] = true;
     } else if (ext_str == "smmpm") {
       extension_table[EXT_SMMPM] = true;
+    } else if (ext_str == "smnpm") {
+      extension_table[EXT_SMNPM] = true;
     } else if (ext_str.substr(0, 3) == "zvl") {
       reg_t new_vlen;
       try {

riscv/isa_parser.h

@@ -83,6 +83,7 @@ typedef enum {
   EXT_ZICFISS,
   EXT_SSDBLTRP,
   EXT_SMMPM,
+  EXT_SMNPM,
   NUM_ISA_EXTENSIONS
 } isa_extension_t;