gas: ginsn: x86: pacify Wmaybe-uininitialized compiler warning

Fix PR binutils/32091

After commit d56083b504, some gcc versions
may warn about unintialized usage of ginsn_func.  Albeit false positive,
adapt the code to escape the warning.

gas/config/
	* tc-i386-ginsn.c (x86_ginsn_indirect_branch): Early exit if
	unexpected args.

gas/config/tc-i386-ginsn.c

@@ -488,6 +488,8 @@ x86_ginsn_indirect_branch (const symbolS *insn_end_sym)
   else if (i.tm.extension_opcode == 2)
     /* 0xFF /2 (call r/m).  */
     ginsn_func = ginsn_new_call;
+  else
+    return ginsn;
 
   if (i.reg_operands)
     {