drm/dp_mst: Tune down error message during payload addition

If a sink is removed in the middle of payload addition the corresponding
AUX transfer will fail as expected, so tune the error message down to a
debug messge.

Cc: Wayne Lin <Wayne.Lin@amd.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230913223218.540365-3-imre.deak@intel.com

drivers/gpu/drm/display/drm_dp_mst_topology.c

@@ -3332,8 +3332,8 @@ int drm_dp_add_payload_part1(struct drm_dp_mst_topology_mgr *mgr,
 
 	ret = drm_dp_create_payload_at_dfp(mgr, payload);
 	if (ret < 0) {
-		drm_warn(mgr->dev, "Failed to create MST payload for port %p: %d\n",
-			 payload->port, ret);
+		drm_dbg_kms(mgr->dev, "Failed to create MST payload for port %p: %d\n",
+			    payload->port, ret);
 		goto put_port;
 	}