Change in coreboot[master]: cannonlake mainboards: Set PMC as hidden in devicetree

[Tim Wawrzynczak (Code Review)]

Attention is currently required from: Nico Huber, Furquan Shaikh, Matt DeVillier, Jeremy Soller, Angel Pons, Michael Niewöhner, Karthik Ramasubramanian.
Tim Wawrzynczak has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/56008 )

Change subject: cannonlake mainboards: Set PMC as hidden in devicetree
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Patch Set 2:

(2 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/56008/comment/53adfa3c_8e68cd94 
PS2, Line 14:
> Were any tests done?

Planning to verify this on google/dratini soon.

Patchset:

PS2:
> "hidden" is not meant to be used with devices but with bridges, where the devices behind that bridge […]

Not true, I wrote the code that switched the meaning of hidden (it was unused at the time in any devicetree, see https://doc.coreboot.org/releases/coreboot-4.13-relnotes.html?highlight=hidd...). This is what TGL, JSL, EKL, and ADL do with their PMC devices, it allows you to use device callbacks on it even though the device is not discoverable during PCI enumeration. CB:41384