Change in coreboot[master]: ec/google/chromeec: Add EC Mux device

[Prashant Malani (Code Review)]

Attention is currently required from: Tim Wawrzynczak, Paul Menzel.
Prashant Malani has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/63792 )

Change subject: ec/google/chromeec: Add EC Mux device
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Patch Set 1:

(2 comments)

Patchset:

PS1:
> > Sure. Which config would be apropriate? `configs/config.google_volteer.build_test_purposes` ? […]

OK. Just to clarify, if I add the devices to the override.cb then I *dont* need to select the Kconfig?

File src/ec/google/chromeec/mux/Kconfig:

https://review.coreboot.org/c/coreboot/+/63792/comment/933a8884_b3f17ed5 
PS1, Line 8: which is used
> I also marked *which*. It’s a contact clause [1]. Anyway, feel free to improve or leave as is. […]

Ack