[ARM] 4783/1: S3C24XX: Add s3c2410_gpio_getpull()

Add the call s3c2410_gpio_getpull() to return the
current state of the pin's pull-up.

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