drm/omap: pass rotation to dispc

The omapdrm driver has not passed the rotation value to the dispc
driver. This doesn't affect RGB formats, but YUV formats don't work
without dispc knowing the orientation.

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