mmix disassemble memory leak

It's a once-off and of no consequence, but fix it anyway.  The mmix
caonoicalize_syms array is an array of pointers.  Freeing it won't
lose symbol names.

	* mmix-dis.c (initialize_mmix_dis_info): Free syms.

opcodes/mmix-dis.c

@@ -117,6 +117,7 @@ initialize_mmix_dis_info (struct disassemble_info *info)
 		  && minfop->reg_name[syms[i]->value] == NULL)
 		minfop->reg_name[syms[i]->value] = syms[i]->name;
 	    }
+	  free (syms);
 	}
     }