[XS] Change in coreboot[master]: mb/google/myst: Add PCIe shutdown workaround

[Jon Murphy (Code Review)]

Attention is currently required from: Eric Lai, Karthik Ramasubramanian, Martin Roth, Paul Menzel, Tim Van Patten.

Jon Murphy has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/75583?usp=email )

Change subject: mb/google/myst: Add PCIe shutdown workaround
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Patch Set 3:

(2 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/75583/comment/5dc47b7a_9cd098ff :
PS3, Line 9: FSP
> Add a version in case FSP gets fixed in the future?

Early bringup, I don't have a version

File src/mainboard/google/myst/port_descriptors.c:

https://review.coreboot.org/c/coreboot/+/75583/comment/e27f2f98_dd3b2b7e :
PS2, Line 56: 	.turn_off_unused_lanes = true,
> What are the differences between the two in terms of unintended side effects? My preference would be […]

It's a workaround.  We're merging this to get through functional testing.  The workaround works.