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>

drivers/mtd/mtdcore.c

@@ -66,7 +66,7 @@ static int mtd_cls_suspend(struct device *dev, pm_message_t state)
 {
 	struct mtd_info *mtd = dev_to_mtd(dev);
 
-	if (mtd->suspend)
+	if (mtd && mtd->suspend)
 		return mtd->suspend(mtd);
 	else
 		return 0;
@@ -76,7 +76,7 @@ static int mtd_cls_resume(struct device *dev)
 {
 	struct mtd_info *mtd = dev_to_mtd(dev);
 	
-	if (mtd->resume)
+	if (mtd && mtd->resume)
 		mtd->resume(mtd);
 	return 0;
 }
@@ -298,6 +298,7 @@ int add_mtd_device(struct mtd_info *mtd)
 			mtd->dev.class = &mtd_class;
 			mtd->dev.devt = MTD_DEVT(i);
 			dev_set_name(&mtd->dev, "mtd%d", i);
+			dev_set_drvdata(&mtd->dev, mtd);
 			if (device_register(&mtd->dev) != 0) {
 				mtd_table[i] = NULL;
 				break;

include/linux/mtd/mtd.h

@@ -251,7 +251,7 @@ struct mtd_info {
 
 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)