V4L/DVB (10946): radio-rtrack2: fix double mutex_unlock

Patch fixes double mutex unlocking.
Signed-off-by: Alexey Klimov <klimov.linux@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/radio/radio-rtrack2.c

@@ -60,7 +60,6 @@ static void rt_mute(struct rtrack2 *dev)
 	mutex_lock(&dev->lock);
 	outb(1, dev->io);
 	mutex_unlock(&dev->lock);
-	mutex_unlock(&dev->lock);
 	dev->muted = 1;
 }