ARM: S5P: Add common S5P GPIO Interrupt support

This patch adds common code to enable support of GPIO interrupt on
S5P SoCs.

The total number of GPIO pins is quite large on S5P SoCs. Registering
irq support for all of them would be a resource waste. Because of that
the interrupt support for standard GPIO pins is registered dynamically
by the s5p_register_gpio_interrupt() function.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
[kgene.kim@samsung.com: minor title fixes]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>