[ARM] S3C24XX: GPIO: Change to macros for GPIO numbering

Prepare to remove the large number of S3C2410_GPxn defines
by moving to S3C2410_GPx(n) in arch/arm.

The following perl was used to change the files:

    perl -pi~ -e 's/S3C2410_GP([A-Z])([0-9]+)([^_^0-9])/S3C2410_GP\1\(\2\)\3/g'

Signed-off-by: Ben Dooks <ben-linux@fluff.org>