drm/sysfb: efidrm: Add EDID support

Enable the connector's EDID property if edid_info contains valid
data. Exports the EDID via sysfs for user-space compositors.

EDID information is not always available. Depending on the system
and kernel configuration, it is either provided by the boot loader
or read by the kernel during early boot stages.

As of now, there's only one EFI display, so that EDID data always
belongs to this output. This might change if there's ever more than
one EFI display in the system.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250401094056.32904-16-tzimmermann@suse.de