S5P: Exynos: Add GPIO pin numbering and rename definitions

S5P: Exynos: Add GPIO pin numbering and rename definitions

This patch includes following changes :
* Adds gpio pin numbering support for EXYNOS SOCs.
  To have consistent 0..n-1 GPIO numbering the banks are divided
  into different parts where ever they have holes in them.

* Rename GPIO definitions from GPIO_... to S5P_GPIO_...
  These changes were done to enable cmd_gpio for EXYNOS and
  cmd_gpio has GPIO_INPUT same as s5p_gpio driver and hence
  getting a error during compilation.

* Adds support for name to gpio conversion in s5p_gpio to enable
  gpio command EXYNOS SoCs. Function has been added to asm/gpio.h
  to decode the input gpio name to gpio number.
  Example: SMDK5420 # gpio set gpa00

Signed-off-by: Leela Krishna Amudala <l.krishna@samsung.com>
Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com>
Signed-off-by: Akshay Saraswat <akshay.s@samsung.com>
Acked-by: Przemyslaw Marczak <p.marczak@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>