drm/omap: dpi: Don't fixup video mode in dpi_set_mode()

The video mode is aleady fixed up by the .check_timings() operation,
there's no need to repeat that when enabling the DPI output.

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>