drm: omapdrm: Move plane info and win out of the plane structure

The plane info and win structures are only used to setup the plane
through the DSS API. Move them from the plane structure to local
variables in omap_plane_setup().

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