ARM: S3C24XX: Add initial s3c_gpio configuration code

Add support for s3c_gpio_setcfg() and s3c_gpio_setpull() implementations
to get ready for removal of the specific code being used by s3c24xx.

Also rename the s3c_gpio_setcfg_s3c24xx_banka to s3c_gpio_setcfg_s3c24xx_a
as seen in the header file to correct a build warning.

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