ARM: S3C: move s3c_device_nand from plat-s3c24xx to plat-s3c

Move the s3c_device_nand platform device from plat-s3c24xx to plat-s3c,
now that the nand driver also support the s3c64xx devices.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>