[XS] Change in coreboot[main]: mb/google/brox/var/greenbayupoc: Add fw_config field for storage

[Shelley Chen (Code Review)]

Attention is currently required from: Eren Peng, Ivan Chen, Nick Vaccaro.

Shelley Chen has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/81833?usp=email )

Change subject: mb/google/brox/var/greenbayupoc: Add fw_config field for storage
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Patch Set 2:

(1 comment)

Patchset:

PS2:
> Maybe we should move it to baseboard if all projects might use it ?

I feel like this would be confusing to people, having some fw_configs in baseboard and some in the actual variant.  Also, this means that when they define the fw_config fields in the variants they'd have to sync with the baseboard FW configs as well.  Do you think that this would be a problem?