drm/i915/mst: Hookup DRM DP MST late_register/early_unregister callbacks

i915 can enable aux device nodes for DP MST by calling
drm_dp_mst_connector_late_register()/
drm_dp_mst_connector_early_unregister(),
so let's hook that up.

Changes since v1:
* Call intel_connector_register/unregister() from
  intel_dp_mst_connector_late_register/unregister() so we don't lose
  error injection - Ville Syrjälä
Changes since v2:
* Don't forget to clean up if intel_connector_register() fails - Ville

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: "Lee, Shawn C" <shawn.c.lee@intel.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200310195122.1590925-1-lyude@redhat.com

drivers/gpu/drm/i915/display/intel_dp_mst.c

@@ -548,12 +548,41 @@ static int intel_dp_mst_get_ddc_modes(struct drm_connector *connector)
 	return ret;
 }
 
+static int
+intel_dp_mst_connector_late_register(struct drm_connector *connector)
+{
+	struct intel_connector *intel_connector = to_intel_connector(connector);
+	int ret;
+
+	ret = drm_dp_mst_connector_late_register(connector,
+						 intel_connector->port);
+	if (ret < 0)
+		return ret;
+
+	ret = intel_connector_register(connector);
+	if (ret < 0)
+		drm_dp_mst_connector_early_unregister(connector,
+						      intel_connector->port);
+
+	return ret;
+}
+
+static void
+intel_dp_mst_connector_early_unregister(struct drm_connector *connector)
+{
+	struct intel_connector *intel_connector = to_intel_connector(connector);
+
+	intel_connector_unregister(connector);
+	drm_dp_mst_connector_early_unregister(connector,
+					      intel_connector->port);
+}
+
 static const struct drm_connector_funcs intel_dp_mst_connector_funcs = {
 	.fill_modes = drm_helper_probe_single_connector_modes,
 	.atomic_get_property = intel_digital_connector_atomic_get_property,
 	.atomic_set_property = intel_digital_connector_atomic_set_property,
-	.late_register = intel_connector_register,
-	.early_unregister = intel_connector_unregister,
+	.late_register = intel_dp_mst_connector_late_register,
+	.early_unregister = intel_dp_mst_connector_early_unregister,
 	.destroy = intel_connector_destroy,
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 	.atomic_duplicate_state = intel_digital_connector_duplicate_state,