drm/omap: Pass both output and display omap_dss_device to connector init

The drm_connector implementation requires access to the omap_dss_device
corresponding to the display, which is passed to its initialization
function and stored internally. Refactoring of the timings operations
will require access to the output omap_dss_device. To prepare for that,
pass it to the connector initialization function and store it internally
as well.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>