x86: Add a generic Intel pinctrl driver

Recent Intel SoCs share a pinctrl mechanism with many common elements. Add
an implementation of this core functionality, allowing SoC-specific
drivers to avoid adding common code.

As well as a pinctrl driver this provides a GPIO driver based on the same
code.

Once other SoCs use this driver we may consider moving more properties to
the device tree (e.g. the community info and pad definitions).

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>