drivers: misc: s400_api: Update S400_SUCCESS_IND to 0xd6

According to latest S400 API doc, the the success indicate value is
changed to 0xd6. So update the driver codes.
Signed-off-by: NYe Li <ye.li@nxp.com>
Signed-off-by: NPeng Fan <peng.fan@nxp.com>

drivers/misc/imx8ulp/imx8ulp_mu.c

@@ -185,7 +185,7 @@ static int imx8ulp_mu_call(struct udevice *dev, int no_resp, void *tx_msg,
 	}
 
 	result = ((struct imx8ulp_s400_msg *)rx_msg)->data[0];
-	if ((result & 0xff) == 0)
+	if ((result & 0xff) == 0xd6)
 		return 0;
 
 	return -EIO;