drm: rcar-du: Enable hotplug detection on HDMI connector

As HDMI support hotplug detection, enable HPD-based poll on HDMI
connectors.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_hdmicon.c

@@ -95,6 +95,7 @@ int rcar_du_hdmi_connector_init(struct rcar_du_device *rcdu,
 	connector = &rcon->connector;
 	connector->display_info.width_mm = 0;
 	connector->display_info.height_mm = 0;
+	connector->polled = DRM_CONNECTOR_POLL_HPD;
 
 	ret = drm_connector_init(rcdu->ddev, connector, &connector_funcs,
 				 DRM_MODE_CONNECTOR_HDMIA);