[ARM] 5054/1: S3C2410: Add GPLv2 license to the s3c2410 serial driver

The original driver had an MODULE_LICENSE statement for GPL,
but no explict license in the header of the file. To make
this more explicit, and since I am the original authour,
we will add a GPLv2 header.

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