ARM: nand: make use of mtd_to_nand() where appropriate

mtd_to_nand() was recently introduced to avoid direct accesses to the
mtd->priv field. Update all ARM specific implementations to use this
helper.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
diff --git a/arch/arm/mach-imx/mach-qong.c b/arch/arm/mach-imx/mach-qong.c
index a213e7b..5c27646 100644
--- a/arch/arm/mach-imx/mach-qong.c
+++ b/arch/arm/mach-imx/mach-qong.c
@@ -131,7 +131,7 @@
  */
 static void qong_nand_cmd_ctrl(struct mtd_info *mtd, int cmd, unsigned int ctrl)
 {
-	struct nand_chip *nand_chip = mtd->priv;
+	struct nand_chip *nand_chip = mtd_to_nand(mtd);
 
 	if (cmd == NAND_CMD_NONE)
 		return;