mtd/nand: s3c6400 support for s3c2410 driver

Add s3c6400 support to the s3c2410 driver. The nand controller in
the s3c64xx devices is compatible with the one in the s3c2412, so
simply reuse that code.

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