tcg/mips: Fix TCG_TARGET_CALL_RET_I128 for o32 abi

The return is by reference, not in 4 integer registers.

This error resulted in

  qemu-system-i386: tcg/mips/tcg-target.c.inc:140: \
    tcg_target_call_oarg_reg: Assertion `slot >= 0 && slot <= 1' failed.

Fixes: 5427a9a7 ("tcg: Add TCG_TARGET_CALL_{RET,ARG}_I128")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/mips/tcg-target.h

@@ -84,13 +84,14 @@ typedef enum {
 #if _MIPS_SIM == _ABIO32
 # define TCG_TARGET_CALL_STACK_OFFSET 16
 # define TCG_TARGET_CALL_ARG_I64      TCG_CALL_ARG_EVEN
+# define TCG_TARGET_CALL_RET_I128     TCG_CALL_RET_BY_REF
 #else
 # define TCG_TARGET_CALL_STACK_OFFSET 0
 # define TCG_TARGET_CALL_ARG_I64      TCG_CALL_ARG_NORMAL
+# define TCG_TARGET_CALL_RET_I128     TCG_CALL_RET_NORMAL
 #endif
 #define TCG_TARGET_CALL_ARG_I32       TCG_CALL_ARG_NORMAL
 #define TCG_TARGET_CALL_ARG_I128      TCG_CALL_ARG_EVEN
-#define TCG_TARGET_CALL_RET_I128      TCG_CALL_RET_NORMAL
 
 /* MOVN/MOVZ instructions detection */
 #if (defined(__mips_isa_rev) && (__mips_isa_rev >= 1)) || \