Make `mainboard_fill_spd_data` mandatory and adapt mainboards to define
this function accordingly.
Change-Id: Ic18c4c574e8c963bbb41c980f43bdbacc57735af
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55806
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>