[S] Change in coreboot[main]: vboot: Add firmware PCR support

[Andrey Pronin (Code Review)]

Attention is currently required from: Andrey Pronin, Christian Walter, Julius Werner, Paul Menzel, Yi Chou, Yu-Ping Wu.

Andrey Pronin has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/79437?usp=email )

Change subject: vboot: Add firmware PCR support
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Patch Set 6:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/79437/comment/c07c4476_c928c633 :
PS6, Line 24: to 10 (and we plan to use PCR 12 for kernel version).
> Well, I don't really see anything specifically talking about two separate PCRs in that doc. […]

double-extension prevention for PCR0 is a very special case. and yes we can implement a special case for this one (stopping at 2 extend ops) if it is ever needed (similarly, hope/expect it's never needed).

so, if we can reduce the # of required PCRs to 1, that'd be great.