Samsung: Move Samsung SoCs GPIO drivers to drivers/gpio

At least s5p100, s5pc110, and s5pc210 (aka exynos4) gpio drivers are moved and merged already.
I want to make a simplified GPIO drivers for Samsung GPIOs.

e.g., most recent (please ignore the old s3c24xx series GPIOs) SoCs use the 4-bit based GPIOs and has 8 pins at each banks. so it can defined as below and use the macro at drivers.

#define SAMSUNG_GPIO(group, n) (((group) * 8) + (n))

enum s5pv210_gpio_groups {
           S5PV210_GPA0,
           S5PV210_GPA1,
           ...
};

SAMSUNG_GPIO(S5PV210_GPA0, n);

In the view of files & directories
drivers/gpio/gpio-samsung.c for generic samsung gpio drivers. pass the required information with platform data. then driver got the platform data and register each gpio groups.
it only defined the how many gpio banks are required and its base address. Of course there's special case, external GPIOs. then we set the flags as SAMSUNG_EXTERNAL_GPIO_FLAGS
and register it as external gpios.

I also consider to use the basic_mmio_gpios but it required to modify and need to expand for our use case since pullup and strength handling. but finally these are also should be moved to proper framework. as it's not defined at generic gpio drivers. Maybe pinmux can handle these.

Do you have any ideas or opinions. then please let me know.

Thank you,
Kyungmin Park