[M] Change in coreboot[master]: mb/google/myst: Enable PCIe devices in devicetree

[Jon Murphy (Code Review)]

Attention is currently required from: Raul Rangel, Tim Van Patten, Karthik Ramasubramanian, Mark Hasemeyer.

Jon Murphy has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/74112 )

Change subject: mb/google/myst: Enable PCIe devices in devicetree
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Patch Set 29:

(1 comment)

File src/mainboard/google/myst/variants/baseboard/devicetree.cb:

https://review.coreboot.org/c/coreboot/+/74112/comment/ea43b7f0_c9463aaa 
PS8, Line 52: 		device ref gpp_bridge_2_4 on end # NVMe
> I misspoke, it's not the lanes, but they are grouping descriptors. […]

My lane mapping in port_descriptors was incorrect, but these are notional naming conventions and can be mapped as we see fit.  The #defines for the dev functions in variants.h help keep us honest with what's mapped here.