drm/sysfb: Add struct drm_sysfb_device

Add struct drm_sysfb_device that stores the system display's hardware
settings. Further helpers for the mode-setting pipeline will use these
fields. Convert ofdrm and simpledrm by embedding the sysfb device in
their device structs.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250401094056.32904-6-tzimmermann@suse.de