ARM: mach-s5p: get rid of all <mach/gpio.h> headers

This renames all the local <mach/gpio.h> headers in the S5P platforms
to <mach/gpio-samsung.h> indicating a scope local to this platform,
and cuts the implicit inclusion of <mach/gpio.h> from <linux/gpio.h>
by removing the use of NEED_MACH_GPIO_H from all S5P variants.

Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>