mtd: rawnand: Use the NAND framework user_conf object for ECC flags

Instead of storing the ECC flags in chip->ecc.options, use
nanddev->ecc.user_conf.flags.

There is currently only one to save: NAND_ECC_MAXIMIZE.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200827085208.16276-21-miquel.raynal@bootlin.com