sim: warnings: fix unused variable warnings

Leave the igen code in place as it's meant to be used with newer
(to-be-written) code ported from the ppc version.

The sh code isn't really necessary as the opcodes enums have been
maintained independently from here, and the lists are out-of-sync
already.

sim/igen/ld-decode.c

@@ -61,12 +61,14 @@ static const name_map decode_combine_map[] = {
   {NULL, 0},
 };
 
+#if 0
 static const name_map decode_search_map[] = {
   {"constants", decode_find_constants},
   {"mixed", decode_find_mixed},
   {"strings", decode_find_strings},
   {NULL, decode_find_mixed},
 };
+#endif
 
 
 static void