tcg: Replace REG_P with arg_loc_reg_p

An inline function is safer than a macro, and REG_P
was rather too generic.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/tcg-internal.h

@@ -58,10 +58,6 @@ typedef struct TCGCallArgumentLoc {
     unsigned tmp_subindex       : 2;
 } TCGCallArgumentLoc;
 
-/* Avoid "unsigned < 0 is always false" Werror, when iarg_regs is empty. */
-#define REG_P(L) \
-    ((int)(L)->arg_slot < (int)ARRAY_SIZE(tcg_target_call_iarg_regs))
-
 typedef struct TCGHelperInfo {
     void *func;
     const char *name;