mtd: mxc_nand: put ecc layout into devtype structs

This commit makes problems on v1 and v2 regarding 4KiBpages more obvious.
As I don't have a 4KiB flash handy I just keep the status quo.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>