drm/bridge: ti-tfp410: Fall back to HPD polling if HPD irq is not available

In case either the HPD gpio is not specified or when the HPD gpio can not
be used as interrupt we should tell the core that the HPD needs to be
polled for detecting hotplug.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190401123342.15767-1-peter.ujfalusi@ti.com