rtc: ds1374: Merge conditional + WARN_ON()

WARN_ON does both these things in one statement.
Using a better pattern with WARN_ON().
Signed-off-by: Srikant Ritolia <s.ritolia@samsung.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/rtc-ds1374.c

@@ -89,10 +89,8 @@ static int ds1374_read_rtc(struct i2c_client *client, u32 *time,
 	int ret;
 	int i;
 
-	if (nbytes > 4) {
-		WARN_ON(1);
+	if (WARN_ON(nbytes > 4))
 		return -EINVAL;
-	}
 
 	ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);