mtd: nand: s3c2440 tacls calculation

Signed-off-by: Fudong Bai <fudongbai@gmail.com>
mtd: nand: s3c2440: keep chip->IO_ADDR_W value intact

This commit fix changed chip->IO_ADDR_W value in hwcontrol routine,
saveenv is working now.

Signed-off-by: Fudong Bai <fudongbai@gmail.com>