drm: omapdrm: Remove the omapdss driver

The omapdss driver (not to be confused with the omapdss_dss driver) is
now a dummy driver with empty probe and remove functions. Remove it.

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