bfd/Dwarf2: gas doesn't mangle names

Include the language identifier emitted by gas in the set of ones where
no mangled names are expected. Even if there could be "hand-mangled"
names, gas doesn't emit DW_AT_linkage_name in the first place.

bfd/dwarf2.c

@@ -1441,6 +1441,7 @@ non_mangled (int lang)
     case DW_LANG_PLI:
     case DW_LANG_UPC:
     case DW_LANG_C11:
+    case DW_LANG_Mips_Assembler:
       return true;
     }
 }