drm/omap: Remove unneeded fallback for missing .check_timings()

drm/omap: Remove unneeded fallback for missing .check_timings()

The .check_timings() operation is present in all panels and connectors.
The fallback that uses .get_timings() in the absence of .check_timings()
is thus unneeded.

While it could be argued that the fallback implements a useful check
that should be extended to cover all fixed-resolution panels, the code
is currently unused and gets in the way of the ongoing refactoring.
Remove it, a similar feature can always be added later.

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>