[ARM] 4779/1: S3C2412: Add s3c2412_gpio_set_sleepcfg() call

Add s3c2412_gpio_set_sleepcfg() to allow the setting of the sleep
configuration of the GPIO blocks.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>