mtd: blkdevs: fix crash related to sysfs attributes.

Remove the attributes group before disk to avoid use after free
Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtd_blkdevs.c

@@ -410,13 +410,14 @@ int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
 		BUG();
 	}
 
-	/* Stop new requests to arrive */
-	del_gendisk(old->disk);
-
 	if (old->disk_attributes)
 		sysfs_remove_group(&disk_to_dev(old->disk)->kobj,
 						old->disk_attributes);
 
+	/* Stop new requests to arrive */
+	del_gendisk(old->disk);
+
+
 	/* Stop the thread */
 	kthread_stop(old->thread);