[ARM] S3C24XX: Fix missing s3c_iis_device.

Commit 52da219e9664e537a745877b0efa7cf2b1ff2996 removed
the s3c_device_iis, but didn't replace it with anything
so a number of s3c24xx machines are currently failing
to build.

As a temporary fix, re-instate s3c_device_iis until a
proper replacement can be done for it.

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