mtd: nand: mxic-ecc: make two read-only arrays static const

Don't populate the read-only arrays possible_strength and
spare_size on the stack but instead make them static
const. Also makes the object code a little smaller.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220307230940.169235-1-colin.i.king@gmail.com