don't download it. keep it in lbmk.

libreboot moved to codeberg for git hosting,
and i didn't want to keep lugging around an
extra git repo just for one tiny project.

When using e.g. -p grub in build/boot/roms, it will
error out. This patch fixes that.

E.g.

./build boot roms t440pmrc_12mb -p grub

Seldom used feature and it was overlooked. Most people
won't use the option that triggered the error.

libre mrc on haswell is quite buggy for now, but works in
a limited fashion

this patch re-adds the old configs, but as _mrc for example
t440p_12mb_mrc instead of t440p_12mb

and t440p_12mb (without _mrc) still uses the libre mrc code

courtesy of Angel Pons from the coreboot project

this uses the following patch set from gerrit, as yet
unmerged (in coreboot master) on this date:

    https://review.coreboot.org/c/coreboot/+/64198/5

logic for downloading mrc blobs has been deleted from
lbmk, as this is now completely obsolete (for haswell
boards)

if other platforms are added later that need mrc.bin,
then logic will be re-added again for that