mtd: rawnand: Make use of the ECC framework

Just enable the ECC framework with raw NAND so that we can drop, one
by one, all the unnecessary/redundant definitions.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200827085208.16276-17-miquel.raynal@bootlin.com