drm/ast: astdp: Validate display modes

Validate each display mode against the astdp transmitter chips. Filters
out modes that the chip does not support.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250204133209.403327-5-tzimmermann@suse.de