mtd: rawnand: marvell: Drop useless line

The raw NAND core now declares the on host ECC engine being the
default if none is provided in the DT. Drop this line doing exactly
the same from the Marvell driver.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20201113124114.449-1-miquel.raynal@bootlin.com