[M] Change in coreboot[main]: soc/mediatek: Remove redundant struct pad_func and PAD_* definitions

[Yidi Lin (Code Review)]

Attention is currently required from: Hung-Te Lin, Xi Chen, Yu-Ping Wu.

Yidi Lin has posted comments on this change by Yidi Lin. ( https://review.coreboot.org/c/coreboot/+/84222?usp=email )

Change subject: soc/mediatek: Remove redundant struct pad_func and PAD_* definitions
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Patch Set 2:

(2 comments)

File src/soc/mediatek/common/include/soc/gpio_common.h:

https://review.coreboot.org/c/coreboot/+/84222/comment/f8cf2911_25135eaa?usp... :
PS2, Line 59: PAD_##name##_FUNC_##func
> These are defined in the `PIN()` macro in gpio_defs. […]

`PIN()` macro of `mt8173` and `mt8183` are different from others SoCs. That's why I exclude `mt8173` and `mt8183` from CB:84221. If you agree, I will move those to `gpio_def.h` and exclude `mt8173` and `mt8183` from refactoring.

https://review.coreboot.org/c/coreboot/+/84222/comment/a396a6f2_73a880d0?usp... :
PS2, Line 59: }
> Is it reasonable to have `GPIO_PULL_DOWN` as the default? I wonder if we could replace `PAD_FUNC` an […]

The driver that uses `PAD_FUNC` either `OMITS` pull_select setting (because it may have external pull up/down resistor depending on the design.) or sets pull_select as they need[1].

`pull_select` is an invalid setting for driver that uses `PAD_FUNC_GPIO`. GPIO pin will disable pull up/down setting eventually. (see `gpio_input` and `gpio_output`)

I prefer keeping existed settings since those settings already passed the SI measurement.

[1]: https://review.coreboot.org/c/coreboot/+/84222/2/src/soc/mediatek/mt8183/i2c...