[media] tw686x: Specify that the DMA is 32 bits

Set vb2_queue.gfp_flags to GFP_DMA32. Otherwise it will start to
create bounce buffers which is something you want to avoid since
those are in limited supply.

Without this patch, DMA scatter-gather may not work because
machines can ran out of buffers easily.
Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/pci/tw686x/tw686x-video.c

@@ -848,6 +848,7 @@ int tw686x_video_init(struct tw686x_dev *dev)
 		vc->vidq.timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
 		vc->vidq.min_buffers_needed = 2;
 		vc->vidq.lock = &vc->vb_mutex;
+		vc->vidq.gfp_flags = GFP_DMA32;
 
 		err = vb2_queue_init(&vc->vidq);
 		if (err) {