mtd: rawnand: marvell: Handle on-die ECC

>From the controllers point of view this is the same as no or
software only ECC.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>