[coreboot-gerrit] Change in coreboot[master]: mb/google/brya: Move PCH selection to variant config

[Felix Singer (Code Review)]

Attention is currently required from: Reka Norman, Subrata Banik, Tim Wawrzynczak, Angel Pons, Nick Vaccaro.
 Felix Singer has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/60378 )

Change subject: mb/google/brya: Move PCH selection to variant config
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Patch Set 3: Code-Review+2