drm/omap: dss: Remove unused omap_dss_driver operations

The .probe(), .remove(), .run_test(), .get_rotate() and .set_rotate()
omap_dss_driver operations are not used. Remove them.

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>