mtd: rawnand: marvell: Use devm_platform_ioremap_res()

Switch from the old platform_get_resource()/devm_ioremap_resource()
couple to the newer devm_platform_ioremap_resource() helper.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200424164501.26719-3-miquel.raynal@bootlin.com