mtd: rawnand: Move the nand_ecc_algo enum to the generic NAND layer

This enumeration is generic and will be reused NAND-wide.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200827085208.16276-4-miquel.raynal@bootlin.com