Change in coreboot[master]: mb/google/mancomb: Add new mainboard

[Felix Held (Code Review)]

Attention is currently required from: Furquan Shaikh, Martin Roth, Mathew King, Paul Menzel, EricR Lai.
Felix Held has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/50007 )

Change subject: mb/google/mancomb: Add new mainboard
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Patch Set 11:

(1 comment)

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

https://review.coreboot.org/c/coreboot/+/50007/comment/c2668515_40d1280a 
PS9, Line 1: # SPDX-License-Identifier: GPL-2.0-or-later
> This mainboard will end up looking a lot like guybrush and we should look for opportunities to move  […]

sharing a devicetree between two different base boards probably creates more trouble than it solves; on zork we had two different devicetrees for the ft5 vs. fp5 based boards. since guybrush and mancomb will be even more different, i'd say that it's a good idea to put them in separate directories.
we do have chipset devicetrees now, so we need to duplicate less things that are common to all boards using the same soc