drm/omap: poll only connectors where the connect/disconnect can be checked

drm/omap: poll only connectors where the connect/disconnect can be checked

When the connector associated detect callback is not provided, we can not
detect if the display is connected or disconnected. These displays do not
support hot plug, they are always connected. Let DRM know that connectors
w/o detect callback should not be polled.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>