mtd: rawnand: ingenic: Make jz4725b_ooblayout_ops static

Fix sparse warning:

drivers/mtd/nand/raw/ingenic/ingenic_nand.c:140:32: warning:
 symbol 'jz4725b_ooblayout_ops' was not declared. Should it be static?

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>