gpio/samsung: gpio-samsung.c to support Samsung GPIOs

This patch adds support for Samsung GPIOs with one gpio driver
and removes old GPIO drivers which are drivers/gpio-s3c24xx.c,
gpio-s3c64xx.c, gpio-s5p64x0.c, gpio-s5pc100.c, gpio-s5pv210.c,
gpio-exynos4.c, gpio-plat-samsung.c, plat-samsung/gpio-config.c
and gpio.c to support each Samsung SoCs before. Because the
gpio-samsung.c can replace old Samsung GPIO drivers.
Basically, the gpio-samsung.c has been made by their merging
and removing duplicated definitions.

Note: gpio-samsung.c includes some SoC dependent codes and it
will be replaced next time.

Cc: Ben Dooks <ben-linux@fluff.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
[kgene.kim@samsung.com: squash the removing and adding patches]
[kgene.kim@samsung.com: fixes bug during to register of gpio_chips]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>