V4L/DVB (13955): cx25821: fix double unlock in medusa_video_init()

medusa_set_videostandard() takes the lock but it always drops it before
returning.

This was found with a static checker and compile tested only.  :/
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/staging/cx25821/cx25821-medusa-video.c

@@ -860,10 +860,8 @@ int medusa_video_init(struct cx25821_dev *dev)
 
 	ret_val = medusa_set_videostandard(dev);
 
-	if (ret_val < 0) {
-		mutex_unlock(&dev->lock);
+	if (ret_val < 0)
 		return -EINVAL;
-	}
 
 	return 1;
 }