mtd: nand: add new ECC mode - ECC_HW_OOB_FIRST

This patch adds the new mode NAND_ECC_HW_OOB_FIRST in the nand code to
support 4-bit ECC on TI DaVinci devices with large page (up to 2KiB) NAND
chips.  This ECC mode is similar to NAND_ECC_HW, with the exception of
read_page API that first reads the OOB area, reads the data in chunks,
feeds the ECC from OOB area to the ECC hw engine and perform any
correction on the data as per the ECC status reported by the engine.

"ECC_HW_OOB_FIRST" name suggested by Thomas Gleixner

Reviewed-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Sneha Narnakaje <nsnehaprabha@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>