This allows to lock down spi among other things Mostly copied from bd82x6x. Tested on Intel DG41WV with the MRC_CACHE driver write protecting the mrc_cache region. Change-Id: If9c3a6118f4586d51c093edec896c347ba904b8f Signed-off-by: Arthur Heymans <arthur@aheymans.xyz> Reviewed-on: https://review.coreboot.org/23358 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Patrick Georgi <pgeorgi@google.com>