drm/bridge/cdns-mhdp8546: Register DP aux channel with userspace

Just adds some missing calls to
drm_dp_aux_register()/drm_dp_aux_unregister() for when we attach/detach the
bridge.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210423184309.207645-2-lyude@redhat.comReviewed-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c

@@ -1719,10 +1719,14 @@ static int cdns_mhdp_attach(struct drm_bridge *bridge,
 
 	dev_dbg(mhdp->dev, "%s\n", __func__);
 
+	ret = drm_dp_aux_register(&mhdp->aux);
+	if (ret < 0)
+		return ret;
+
 	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
 		ret = cdns_mhdp_connector_init(mhdp);
 		if (ret)
-			return ret;
+			goto aux_unregister;
 	}
 
 	spin_lock(&mhdp->start_lock);
@@ -1738,6 +1742,9 @@ static int cdns_mhdp_attach(struct drm_bridge *bridge,
 		       mhdp->regs + CDNS_APB_INT_MASK);
 
 	return 0;
+aux_unregister:
+	drm_dp_aux_unregister(&mhdp->aux);
+	return ret;
 }
 
 static void cdns_mhdp_configure_video(struct cdns_mhdp_device *mhdp,
@@ -2082,6 +2089,8 @@ static void cdns_mhdp_detach(struct drm_bridge *bridge)
 
 	dev_dbg(mhdp->dev, "%s\n", __func__);
 
+	drm_dp_aux_unregister(&mhdp->aux);
+
 	spin_lock(&mhdp->start_lock);
 
 	mhdp->bridge_attached = false;