tcg/mips: implement the not_i32 op the same way as gcc

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
diff --git a/tcg/mips/tcg-target.c b/tcg/mips/tcg-target.c
index a0c5289..7744281 100644
--- a/tcg/mips/tcg-target.c
+++ b/tcg/mips/tcg-target.c
@@ -1243,7 +1243,7 @@
         tcg_out_opc_reg(s, OPC_NOR, args[0], args[1], args[2]);
         break;
     case INDEX_op_not_i32:
-        tcg_out_opc_reg(s, OPC_NOR, args[0], args[1], args[1]);
+        tcg_out_opc_reg(s, OPC_NOR, args[0], TCG_REG_ZERO, args[1]);
         break;
     case INDEX_op_xor_i32:
         if (const_args[2]) {