[XL] Change in coreboot[main]: mb/google/brox: Create jubilant variant

[Karthik Ramasubramanian (Code Review)]

Attention is currently required from: Bob Moragues, Bob Moragues, David Wu, Ren Kuo, Shelley Chen, Subrata Banik, Tyler Wang, YH Lin.

Karthik Ramasubramanian has posted comments on this change by Ren Kuo. ( https://review.coreboot.org/c/coreboot/+/83212?usp=email )

Change subject: mb/google/brox: Create jubilant variant
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Patch Set 30: Code-Review+2