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-pxa/balloon3.c b/arch/arm/mach-pxa/balloon3.c
index a727282..7734ec4 100644
--- a/arch/arm/mach-pxa/balloon3.c
+++ b/arch/arm/mach-pxa/balloon3.c
@@ -572,7 +572,7 @@
 #if defined(CONFIG_MTD_NAND_PLATFORM)||defined(CONFIG_MTD_NAND_PLATFORM_MODULE)
 static void balloon3_nand_cmd_ctl(struct mtd_info *mtd, int cmd, unsigned int ctrl)
 {
-	struct nand_chip *this = mtd->priv;
+	struct nand_chip *this = mtd_to_nand(mtd);
 	uint8_t balloon3_ctl_set = 0, balloon3_ctl_clr = 0;
 
 	if (ctrl & NAND_CTRL_CHANGE) {