tcg/i386: Set P_REXW in tcg_out_addi_ptr

The REXW bit must be set to produce a 64-bit pointer result; the
bit is disabled in 32-bit mode, so we can do this unconditionally.

Fixes: 7d9e1ee ("tcg/i386: Adjust assert in tcg_out_addi_ptr")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1592
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1642
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
(cherry picked from commit 9889985)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

tcg/i386/tcg-target.c.inc

@@ -1083,7 +1083,7 @@ static void tcg_out_addi_ptr(TCGContext *s, TCGReg rd, TCGReg rs,
 {
     /* This function is only used for passing structs by reference. */
     tcg_debug_assert(imm == (int32_t)imm);
-    tcg_out_modrm_offset(s, OPC_LEA, rd, rs, imm);
+    tcg_out_modrm_offset(s, OPC_LEA | P_REXW, rd, rs, imm);
 }
 
 static inline void tcg_out_pushi(TCGContext *s, tcg_target_long val)