drm/ast: Validate DRM display modes against VBIOS modes

drm/ast: Validate DRM display modes against VBIOS modes

Test DRM display modes against the list of modes supported by the
VBIOS. The helper will respect the supported-modes flags in struct
ast_device. Hence only DRM display modes supported by the VBIOS
will be reported; without the current duplication of this information.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250131092257.115596-12-tzimmermann@suse.de