ARM: S3C2440: Fix SMDK2440 SoC selection

Fix the entries for SMDK2440 should have allowed for S3C2440 or S3C2440
SoC selection but this depended on ARCH_S3C2440 which has not been around
for a while.

Remove the dependency to allow this to be selected.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>