Change in coreboot[master]: mb/prodrive/hermes: Map PCIe clocks to root ports

[Angel Pons (Code Review)]

Attention is currently required from: Patrick Rudolph, Christian Walter, Felix Held.
Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/58368 )

Change subject: mb/prodrive/hermes: Map PCIe clocks to root ports
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Patch Set 2:

(1 comment)

File src/mainboard/prodrive/hermes/devicetree.cb:

https://review.coreboot.org/c/coreboot/+/58368/comment/f2a0f4f0_e113bdd0 
PS2, Line 30: 	register "PcieClkSrcUsage[0]" = "20"		# PCIe Slot1
> might be good to have defines or depending on what this actually does an enum in the soc code for th […]

I'll address this in a follow-up. I'd like to properly abstract the clock source and clock request settings with a struct.