ARM: S5PC1xx: add gpiolib and external/gpio interrupt support

Add support for gpiolib calls. This is based on the gpiolib implementation
from plat-s3c64xx tree.
Add support for external interrupts for GPIO H banks.
Add support for GPIO interrupts for all banks.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>