mtd: use dev_of_node helper in mtd_get_of_node

This allows better compile-time optimizations with CONFIG_OF disabled.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

include/linux/mtd/mtd.h

@@ -393,7 +393,7 @@ static inline void mtd_set_of_node(struct mtd_info *mtd,
 
 static inline struct device_node *mtd_get_of_node(struct mtd_info *mtd)
 {
-	return mtd->dev.of_node;
+	return dev_of_node(&mtd->dev);
 }
 
 static inline int mtd_oobavail(struct mtd_info *mtd, struct mtd_oob_ops *ops)