S3C24XX: GPIO: Fix pin range check in s3c_gpiolib_getchip

In the s3c_gpiolib_getchip implementation for s3c24xx the check whether a pin is
in the gpio banks range is reversed. Thus the function returns NULL for valid
pins and the gpio chip if its not valid.

As a result gpio states are not saved/restored properly during suspend/resume.

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