mtd: rawnand: meson: support for 512B ECC step size

Meson NAND supports both 512B and 1024B ECC step size.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230717053402.1203724-3-AVKrasnov@sberdevices.ru