[ARM] 3284/1: S3C2400 - adds support to GPIO

Patch from Lucas Correia Villa Real

This patch adds support to GPIO on the S3C2400, which is going to
be used by the GP32 machine and the SMDK2400 development board.

Signed-off-by: Lucas Correia Villa Real <lucasvr@gobolinux.org>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>