[ARM] 3636/1: S3C2412: Add selection of CPU_ARM926

Patch from Ben Dooks

Select CONFIG_CPU_ARM926 when CONFIG_CPU_S3C2412 is
selected.

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