[ARM] 2976/1: S3C2410: add static to functions in serial driver

Patch from Ben Dooks

The s3c2410 serial driver is missing static declerations
on several functions that are not exported, and have no
need of being exported outside the driver

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