Use the nand_to_mtd() helper to access chip->mtd as done everywhere
else.
Signed-off-by: NBoris Brezillon <bbrezillon@kernel.org>
Signed-off-by: NMiquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: NFrieder Schrempf <frieder.schrempf@kontron.de>