pinctrl: add AMD GPIO driver support.

KERNCZ GPIO is a new IP from AMD. it can be implemented in both x86 and ARM.
Current driver patch only support GPIO in x86.

Signed-off-by: Ken Xue <Ken.Xue@amd.com>
[Moved back to <linux/gpio.h> header]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>