[media] tw5864: constify vb2_ops structure

Inspired by "[media] pci: constify vb2_ops structures" patch
from Julia Lawall (dated 9 Sep 2016).
Signed-off-by: NAndrey Utkin <andrey.utkin@corp.bluecherry.net>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/pci/tw5864/tw5864-video.c

@@ -465,7 +465,7 @@ static void tw5864_stop_streaming(struct vb2_queue *q)
 	spin_unlock_irqrestore(&input->slock, flags);
 }
 
-static struct vb2_ops tw5864_video_qops = {
+static const struct vb2_ops tw5864_video_qops = {
 	.queue_setup = tw5864_queue_setup,
 	.buf_queue = tw5864_buf_queue,
 	.start_streaming = tw5864_start_streaming,