[media] vb2: fix streamoff handling if streamon wasn't called

If you request buffers, then queue buffers and then call STREAMOFF
those buffers are not returned to their dequeued state because streamoff
will just return if q->streaming was 0.

This means that afterwards you can never QBUF that same buffer again unless
you do STREAMON, REQBUFS or close the filehandle first.

It is clear that if you do STREAMOFF even if no STREAMON was called before,
you still want to have all buffers returned to their proper dequeued state.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

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

@@ -2125,14 +2125,14 @@ static int vb2_internal_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
 		return -EINVAL;
 	}
 
-	if (!q->streaming) {
-		dprintk(3, "streamoff successful: not streaming\n");
-		return 0;
-	}
-
 	/*
 	 * Cancel will pause streaming and remove all buffers from the driver
 	 * and videobuf, effectively returning control over them to userspace.
+	 *
+	 * Note that we do this even if q->streaming == 0: if you prepare or
+	 * queue buffers, and then call streamoff without ever having called
+	 * streamon, you would still expect those buffers to be returned to
+	 * their normal dequeued state.
 	 */
 	__vb2_queue_cancel(q);