V4L/DVB (12372): saa7134: fix lock imbalance

There seems to be one superfluos unlock in a poll function. Remove it.
Signed-off-by: NJiri Slaby <jirislaby@gmail.com>
Signed-off-by: NDouglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/saa7134/saa7134-video.c

@@ -1444,7 +1444,6 @@ video_poll(struct file *file, struct poll_table_struct *wait)
 			fh->cap.ops->buf_queue(&fh->cap,fh->cap.read_buf);
 			fh->cap.read_off = 0;
 		}
-		mutex_unlock(&fh->cap.vb_lock);
 		buf = fh->cap.read_buf;
 	}