[media] uvcvideo: small cleanup in uvc_video_clock_update()

Smatch is not smart enough to see that "&stream->clock.lock" and
"&clock->lock" are the same thing so it complains about the locking
here.  Let's make it more consistent.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/usb/uvc/uvc_video.c

@@ -706,7 +706,7 @@ void uvc_video_clock_update(struct uvc_streaming *stream,
 	vbuf->vb2_buf.timestamp = timespec_to_ns(&ts);
 
 done:
-	spin_unlock_irqrestore(&stream->clock.lock, flags);
+	spin_unlock_irqrestore(&clock->lock, flags);
 }
 
 /* ------------------------------------------------------------------------