[media] si2157: add one missing parenthesis

Fix following warnings:
si2157_cmd_execute() warn: add some parenthesis here?
si2157_cmd_execute() warn: maybe use && instead of &

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/tuners/si2157.c

@@ -57,7 +57,7 @@ static int si2157_cmd_execute(struct si2157 *s, struct si2157_cmd *cmd)
 			jiffies_to_msecs(jiffies) -
 			(jiffies_to_msecs(timeout) - TIMEOUT));
 
-	if (!(buf[0] >> 7) & 0x01) {
+	if (!((buf[0] >> 7) & 0x01)) {
 		ret = -ETIMEDOUT;
 		goto err_mutex_unlock;
 	} else {