ARM: EXYNOS: add support GPIO for EXYNOS5250

This patch adds support regarding GPIO definitions for
EXYNOS5250 and change the macro of GPIO numbering to use
EXYNOS4 and EXYNOS5 SoCs.

Signed-off-by: Sangsu Park <sangsu4u.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>