simple-dmabuf-v4l: Remove incorrect assert

According to v4l2 documentation, DQBUF always clears FLAG_DONE, so
this assert can be expected to fire 100% of the time.

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/clients/simple-dmabuf-v4l.c b/clients/simple-dmabuf-v4l.c
index b49d62f..82b55a9 100644
--- a/clients/simple-dmabuf-v4l.c
+++ b/clients/simple-dmabuf-v4l.c
@@ -457,8 +457,6 @@
 		return -1;
 	}
 
-	assert(buf.flags & V4L2_BUF_FLAG_DONE);
-
 	return buf.index;
 }