mtd: nand: make use of mtd_to_nand() in NAND drivers

mtd_to_nand() was recently introduced to avoid direct accesses to the
mtd->priv field. Update all NAND drivers to use it.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
diff --git a/drivers/mtd/nand/nuc900_nand.c b/drivers/mtd/nand/nuc900_nand.c
index f0687f7..8148cd6 100644
--- a/drivers/mtd/nand/nuc900_nand.c
+++ b/drivers/mtd/nand/nuc900_nand.c
@@ -136,7 +136,7 @@
 static void nuc900_nand_command_lp(struct mtd_info *mtd, unsigned int command,
 				   int column, int page_addr)
 {
-	register struct nand_chip *chip = mtd->priv;
+	register struct nand_chip *chip = mtd_to_nand(mtd);
 	struct nuc900_nand *nand;
 
 	nand = container_of(mtd, struct nuc900_nand, mtd);