mtd: nand: make use of mtd_to_nand() in NAND core code

mtd_to_nand() was recently introduced to avoid direct access to the
mtd->priv field. Update core code to use mtd_to_nand().

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/nand_bch.c

@@ -52,7 +52,7 @@ struct nand_bch_control {
 int nand_bch_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
 			   unsigned char *code)
 {
-	const struct nand_chip *chip = mtd->priv;
+	const struct nand_chip *chip = mtd_to_nand(mtd);
 	struct nand_bch_control *nbc = chip->ecc.priv;
 	unsigned int i;
 
@@ -79,7 +79,7 @@ EXPORT_SYMBOL(nand_bch_calculate_ecc);
 int nand_bch_correct_data(struct mtd_info *mtd, unsigned char *buf,
 			  unsigned char *read_ecc, unsigned char *calc_ecc)
 {
-	const struct nand_chip *chip = mtd->priv;
+	const struct nand_chip *chip = mtd_to_nand(mtd);
 	struct nand_bch_control *nbc = chip->ecc.priv;
 	unsigned int *errloc = nbc->errloc;
 	int i, count;