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/jz4740_nand.c b/drivers/mtd/nand/jz4740_nand.c
index 5a99a93..5a06fba 100644
--- a/drivers/mtd/nand/jz4740_nand.c
+++ b/drivers/mtd/nand/jz4740_nand.c
@@ -82,7 +82,7 @@
 static void jz_nand_select_chip(struct mtd_info *mtd, int chipnr)
 {
 	struct jz_nand *nand = mtd_to_jz_nand(mtd);
-	struct nand_chip *chip = mtd->priv;
+	struct nand_chip *chip = mtd_to_nand(mtd);
 	uint32_t ctrl;
 	int banknr;
 
@@ -104,7 +104,7 @@
 static void jz_nand_cmd_ctrl(struct mtd_info *mtd, int dat, unsigned int ctrl)
 {
 	struct jz_nand *nand = mtd_to_jz_nand(mtd);
-	struct nand_chip *chip = mtd->priv;
+	struct nand_chip *chip = mtd_to_nand(mtd);
 	uint32_t reg;
 	void __iomem *bank_base = nand->bank_base[nand->selected_bank];