[media] vb2: V4L2_BUF_FLAG_DONE is set after DQBUF

According to the doc, V4L2_BUF_FLAG_DONE is cleared after DQBUF:

V4L2_BUF_FLAG_DONE 0x00000004  ... After calling the VIDIOC_QBUF or
VIDIOC_DQBUF it is always cleared ...

Unfortunately, it seems that videobuf2 keeps it set after DQBUF. This
can be tested with vivid and dev_debug:

[257604.338082] video1: VIDIOC_DQBUF: 71:33:25.00260479 index=3,
type=vid-cap, flags=0x00002004, field=none, sequence=163,
memory=userptr, bytesused=460800, offset/userptr=0x344b000,
length=460800

This patch forces FLAG_DONE to 0 after calling DQBUF.

Reported-by: Dimitrios Katsaros <patcherwork@gmail.com>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/v4l2-core/videobuf2-v4l2.c

@@ -633,6 +633,12 @@ static int vb2_internal_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b,
 
 	ret = vb2_core_dqbuf(q, NULL, b, nonblocking);
 
+	/*
+	 *  After calling the VIDIOC_DQBUF V4L2_BUF_FLAG_DONE must be
+	 *  cleared.
+	 */
+	b->flags &= ~V4L2_BUF_FLAG_DONE;
+
 	return ret;
 }