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

[Jon Murphy (Code Review)]

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

Jon Murphy has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/74093 )

Change subject: mb/google/myst: Add new mainboard
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Patch Set 3:

(1 comment)

File src/mainboard/google/myst/dsdt.asl:

https://review.coreboot.org/c/coreboot/+/74093/comment/f25ec650_7a4b2e62 
PS2, Line 1: /* SPDX-License-Identifier: GPL-2.0-only */
> Is there a Myst version of this spreadsheet that we should be tracking these CLs with? […]

The Myst doc is meant to capture the entire process.  I haven't added the Myst coreboot CL's yet, but the stack matches the Skyrim stack.