tcg/mips: Unify TCG_GUEST_BASE_REG tests

In tcg_out_qemu_ld/st, we already check for guest_base matching int16_t.
Mirror that when setting up TCG_GUEST_BASE_REG in the prologue.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/mips/tcg-target.c.inc

@@ -2312,7 +2312,7 @@ static void tcg_target_qemu_prologue(TCGContext *s)
     }
 
 #ifndef CONFIG_SOFTMMU
-    if (guest_base) {
+    if (guest_base != (int16_t)guest_base) {
         tcg_out_movi(s, TCG_TYPE_PTR, TCG_GUEST_BASE_REG, guest_base);
         tcg_regset_set_reg(s->reserved_regs, TCG_GUEST_BASE_REG);
     }