ARM: OMAP2+: gpmc: nand register helper bch update

Update helper function that provides gpmc-nand register
details for nand driver with bch register information.
Using this nand driver can be made self sufficient to
handle remaining gpmc-nand operations by itself instead
of relying on gpmc exported nand functions.

Signed-off-by: Afzal Mohammed <afzal@ti.com>