Identical to the existing 2412/2443 support except for the base address
and NFCONF value (bit 2 is reserved and should be written as 1 ref UM).

Tested on a s3c6410 board, but controller is identical in 6400/6410
except for 8bit MLC ECC support in 6410 which isn't supported by the
driver.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>