drm/dp/mst: reply with ACK for UP reqs

Currently we reply with NACK to UP requests which might
confuse receivers. We haven't seen any actual issues with
this but should still respond to UP requests correctly.
Signed-off-by: Mykola Lysenko <Mykola.Lysenko@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449514552-10236-2-git-send-email-harry.wentland@amd.comSigned-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_dp_mst_topology.c

@@ -1823,7 +1823,7 @@ static int drm_dp_encode_up_ack_reply(struct drm_dp_sideband_msg_tx *msg, u8 req
 {
 	struct drm_dp_sideband_msg_reply_body reply;
 
-	reply.reply_type = 1;
+	reply.reply_type = 0;
 	reply.req_type = req_type;
 	drm_dp_encode_sideband_reply(&reply, msg);
 	return 0;