kmeter1_nand: allow uasge of NAND_ECC_SOFT_BCH

If CONFIG_NAND_ECC_BCH is set we use 4-bit error corretion code
instead of the 1-bit error correction code on the NAND device
within this driver.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Acked-by: Scott Wood <scottwood@freescale.com>