drm/omap: remove no-op cleanup code

The driver sets crtc and plane rotation properties back to 0 degrees in
dev_lastclose() using drm_object_property_set_value().
drm_object_property_set_value() doesn't do anything with atomic drivers,
and a recent change added WARN_ON() when atomic driver calls the
function.

So remove the code.

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