Move machine specific code to board at s3c64xx (v2)

Move machine specific code to board at s3c64xx (v2)

Move machine specific code to smdk6400.
Some board use OneNAND instead of NAND.

Some register MP0_CS_CFG[5:0] are controled by both h/w and s/w.
So it's better to use macro instead of hard-coded value.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>