NAND: sync with 2.6.27

This brings the core NAND code up to date with the Linux kernel.

Since there were several drivers in Linux as of the last update that are
not in u-boot, I'm not bringing over new drivers that have been added
since in the absence of an interested party.

I did not update OneNAND since it was recently synced by Kyungmin Park,
and I'm not sure exactly what the common ancestor is.

Signed-off-by: Scott Wood <scottwood@freescale.com>