[XS] Change in coreboot[main]: mb/google/brya/var/xol: Disable unused controllers

[Subrata Banik (Code Review)]

Attention is currently required from: Dinesh Gehlot, Eric Lai, Kapil Porwal, Nick Vaccaro, SH Kim.

Subrata Banik has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/81105?usp=email )

Change subject: mb/google/brya/var/xol: Disable unused controllers
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Patch Set 1:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/81105/comment/a7755940_df3cc335 :
PS1, Line 14: - PCIE RP8
            : - PCIE RP9
> Yeah, I understand your remark, it must be a more powerful way to disable PCIe RP.
> RP8 is under PCIe 5-8 group and PR9 is under PCIe 9-12. Currently PCIe 5-8 is set as 4x1 and PCIe 9-12 is set as 1x4. It's following baseboard config.
> I'd like to keep current softstrap for future. I believe the runtime job to disable PCIe RPs in coreboot/FSP is not a big deal. Now we are under proto stage, there is a posibility to support another device through PCIe port in future. Then we only need coreboot change for it.

sure, let's keep this for future if possible.