[M] Change in coreboot[main]: tree: Rename CBFS_SIZE to BIOS_SIZE

[Angel Pons (Code Review)]

Attention is currently required from: Alexander Couzens, Alicja Michalska, Christian Walter, Dinesh Gehlot, Eran Mitrani, Erik van den Bogaert, Felix Held, Frans Hendriks, Fred Reitberger, Intel coreboot Reviewers, Jakub "Kuba" Czapiga, Jason Glenesk, Jason Nien, Jayvik Desai, Jeremy Soller, Jonathon Hall, Kapil Porwal, Martin L Roth, Martin Roth, Maxim Polyakov, Michael Niewöhner, Michał Kopeć, Michał Żygowski, Nicholas Chin, Nick Vaccaro, Patrick Rudolph, Piotr Król, Pranava Y N, Shuo Liu, Stefan Ott, Subrata Banik, Tarun, Tim Crawford, Werner Zeh.

Angel Pons has posted comments on this change by Shuo Liu. ( https://review.coreboot.org/c/coreboot/+/86571?usp=email )

Change subject: tree: Rename CBFS_SIZE to BIOS_SIZE
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Patch Set 5: Code-Review-1

(1 comment)

Patchset:

PS5: 
I can't think of any descriptive names for this option that are good enough to justify breaking custom configs. If anything, I'd be okay updating the prompt and/or the help text as those are the most user-visible and don't impact the rest of the codebase.

IIRC this originally *was* the CBFS size, but things changed a bit with the introduction of fmap: CBFS necessarily has to be smaller than `CBFS_SIZE` because at least the fmap structures have to fit in there as well. I imagine that, for backwards compatibility reasons, this option got repurposed and is now the size of coreboot as a whole in the flash chip (which was the case before, when CBFS was the topmost level structure). So a pre-fmap config specifying some value for `CBFS_SIZE` would still use the exact same amount of space in flash after fmap got introduced.

...thinking too much about it, one could say that `CBFS_SIZE` now specifies the allotted size of "coreboot's fancy shenanigans" (CBFS) in flash. Sooo... Perhaps we don't have to rename this option after all? :^)