Change in coreboot[master]: soc/intel/common: Add `struct gpio_pad_table` and helpers

[Angel Pons (Code Review)]

Attention is currently required from: Furquan Shaikh, Subrata Banik, Michael Niewöhner, Patrick Rudolph.
Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/50176 )

Change subject: soc/intel/common: Add `struct gpio_pad_table` and helpers
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Patch Set 1:

(2 comments)

File src/soc/intel/common/block/include/intelblocks/gpio.h:

https://review.coreboot.org/c/coreboot/+/50176/comment/3c749d34_80236c67 
PS1, Line 75: 	const struct pad_config *padcfg;
            : 	size_t length;
            :
> modifying padcfg and not adapting the lenght could (will?) lead to problems; what about making both  […]

Hmmm, good point. If anything, the current `const` usage is a bit stupid: you can't modify the pad_config values (it's a pointer to `const`struct pad_config`), but you're free to replace the pointer and mess with the `length` value... :D

https://review.coreboot.org/c/coreboot/+/50176/comment/dfa7165d_c50276fb 
PS1, Line 78: (struct gpio_pad_table)
> this cast isn't needed

The cast is there on purpose to allow this usage:

const struct pad_config pad_array[] = {
    ...
 };
 gpio_configure_pad_table(GPIO_PAD_ARRAY(pad_array));