[M] Change in coreboot[master]: mb/google/myst: Enable AP <-> GSC communication

[Tim Van Patten (Code Review)]

Attention is currently required from: Raul Rangel, Jon Murphy, Karthik Ramasubramanian, Mark Hasemeyer.

Tim Van Patten has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/74111 )

Change subject: mb/google/myst: Enable AP <-> GSC communication
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Patch Set 8:

(2 comments)

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

https://review.coreboot.org/c/coreboot/+/74111/comment/f8d5262c_52c8f98d 
PS8, Line 136: 			device i2c 50 on end
Do we need the `alias ti50`?

```
device i2c 50 alias ti50 on end
```

File src/mainboard/google/myst/variants/baseboard/gpio.c:

https://review.coreboot.org/c/coreboot/+/74111/comment/9ac72606_c99d951a 
PS8, Line 178: 	PAD_NF(GPIO_113, I2C2_SCL, PULL_NONE),
go/myst-gpios doesn't list these GPIOs (113, 114). Where did they come from?