drivers/mrc_cache: Always generate an FMAP region

This automatically generates an FMAP region for the MRC_CACHE driver
which is easier to handle than a cbfsfile.

Adds some spaces and more comments to Makefile.inc to improve
readability.

Tested on Thinkpad x200 with some proof of concept patches.

Change-Id: Iaaca36b1123b094ec1bbe5df4fb25660919173ca
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/23150
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
6 files changed