nand: mxs: Fix for calculating ecc strength on some types of NAND flash
Was tested on NAND with {writesize=4096, oobsize=224} and
{writesize=2048, oobsize=64}.
This patch will not break any NAND that was working
before. Implemented calculation way may be used for other NAND chips
with writesize == 2048 but oobsize != 64.
Signed-off-by: Dmitry Lavnikevich <d.lavnikevich@sam-solutions.com>
Signed-off-by: Grigory Milev <g.milev@sam-solutions.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>