[ARM] 3806/2: S3C2412: Fix GPIO VA when only S3C2412 selected

The s3c24xx_va_gpio2 variable is only used
when the S3C2412 and another cpu-type is
being used in the kernel. This patch ensures
it is not set when it is not being used.

Fixes bug report by Thomas Gleixner.

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