FYI: CBFS metadata caching landed, let me know if something breaks

[Julius Werner]

I just landed a somewhat large-ish feature that enables CBFS metadata
caching across most boards (this will avoid reloading CBFS file
headers from flash on every file lookup and ultimately increase boot
speed): https://review.coreboot.org/c/coreboot/+/38424

I wrote and tested it best as I could, but with the pandemic my access
to different test platforms is limited. If anyone sees their platform
break starting with this patch, please let me know, and if you need a
quick fix just add `select NO_CBFS_MCACHE` to the respective
board/platform Kconfig (this effectively disables the feature but
without having to revert the whole patch and potential dependencies
back out).