Change in coreboot[master]: ec/google/chromeec: Provide EC access for Retimer firmware update

[Tim Wawrzynczak (Code Review)]

Attention is currently required from: John Zhao, Duncan Laurie, Brandon Breitenstein, Rajmohan Mani.
Tim Wawrzynczak has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/49257 )

Change subject: ec/google/chromeec: Provide EC access for Retimer firmware update
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Patch Set 5:

(1 comment)

File src/ec/google/chromeec/ec_acpi.c:

https://review.coreboot.org/c/coreboot/+/49257/comment/d82d6f03_88459971 
PS4, Line 242: \_SB_.PCI0.LPCB.EC0_.
> I initially followed the exact ways from your guideline.  […]

You have an extra pnp 0c09 device, that might prevent the alias from taking effect?, e.g.:

volteer/baseboard/devicetree.cb:
```
device ref pch_espi on
    chip ec/google/chromeec
        device pnp 0c09.0 alias chromeec on end
    end
end
```