ARM: s3c: fix check of index into s3c_gpios[]

The check of the s3c_gpios[] index had an off-by-one.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Acked-by: Ben Dooks <ben-linux@fluff.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>