[XL] Change in coreboot[main]: soc/mediatek/mt8196: Add GPIO driver

[Yu-Ping Wu (Code Review)]

Attention is currently required from: Hung-Te Lin, Jarried Lin, Paul Menzel.

Yu-Ping Wu has posted comments on this change by Jarried Lin. ( https://review.coreboot.org/c/coreboot/+/83922?usp=email )

Change subject: soc/mediatek/mt8196: Add GPIO driver
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Patch Set 6:

(1 comment)

File src/soc/mediatek/mt8196/include/soc/gpio_base.h:

PS4:
> This .h file is included by common/soc, but 8173 uses a different gpio_base from the others.  […]

MT8173 has an even simpler definition:

```
typedef struct {
    u32 id;
} gpio_t;
```

The maximum ID for MT8173 is 134, so 8 bits should be enough for the `id` field. That means MT8173 can use this shared `gpio_t` as well. It just doesn't use the other fields.