mtd: rawnand: Rename the ECC algorithm enumeration items

NAND_ECC_ is not a meaningful prefix, use NAND_ECC_ALGO_ instead.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200827085208.16276-3-miquel.raynal@bootlin.com