V4L/DVB (10270): saa7146: fix unbalanced mutex_lock/unlock

The default case of the switch didn't unlock the mutex.
Signed-off-by: NHans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/common/saa7146_video.c

@@ -576,6 +576,7 @@ static int set_control(struct saa7146_fh *fh, struct v4l2_control *c)
 		vv->vflip = c->value;
 		break;
 	default: {
+		mutex_unlock(&dev->lock);
 		return -EINVAL;
 	}
 	}