[S] Change in coreboot[main]: mb/google/brya: Create yavista variant

[Henry Sun (Code Review)]

Attention is currently required from: Derek Huang, Eric Lai, Kapil Porwal, Nick Vaccaro, Paul Menzel, Rasheed Hsueh, Subrata Banik.

Henry Sun has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/80342?usp=email )

Change subject: mb/google/brya: Create yavista variant
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Patch Set 5: Code-Review-1

(1 comment)

Patchset:

PS5: 
Hi Rash, Yavista should be under Nissa instead of Brya, please confirm or follow up. Thanks!