mtd: fix the conversion from dev to mtd_info

The patch fixes a bug when converting dev to mtd_info by using the
drvdata of the dev, the previous code used
container_of(dev, struct mtd_info, dev), but won't work for the mtdXro
devices as they created without being contained inside mtd_info structure.

Signed-off-by: Saeed Bishara <saeed@marvell.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 5675b63..0f32a9b 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -251,7 +251,7 @@
 
 static inline struct mtd_info *dev_to_mtd(struct device *dev)
 {
-	return dev ? container_of(dev, struct mtd_info, dev) : NULL;
+	return dev ? dev_get_drvdata(dev) : NULL;
 }
 
 static inline uint32_t mtd_div_by_eb(uint64_t sz, struct mtd_info *mtd)