mtd: grab a reference to the MTD of_node before registering it

We now stick the device node representing the current MTD (if any) into
sysfs, so let's make sure we have a reference to it before doing that.
Suggested-by: NBoris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>
Reviewed-by: NBoris Brezillon <boris.brezillon@free-electrons.com>

drivers/mtd/mtdcore.c

@@ -32,6 +32,7 @@
 #include <linux/err.h>
 #include <linux/ioctl.h>
 #include <linux/init.h>
+#include <linux/of.h>
 #include <linux/proc_fs.h>
 #include <linux/idr.h>
 #include <linux/backing-dev.h>
@@ -454,6 +455,7 @@ int add_mtd_device(struct mtd_info *mtd)
 	mtd->dev.devt = MTD_DEVT(i);
 	dev_set_name(&mtd->dev, "mtd%d", i);
 	dev_set_drvdata(&mtd->dev, mtd);
+	of_node_get(mtd_get_of_node(mtd));
 	error = device_register(&mtd->dev);
 	if (error)
 		goto fail_added;
@@ -476,6 +478,7 @@ int add_mtd_device(struct mtd_info *mtd)
 	return 0;
 
 fail_added:
+	of_node_put(mtd_get_of_node(mtd));
 	idr_remove(&mtd_idr, i);
 fail_locked:
 	mutex_unlock(&mtd_table_mutex);
@@ -517,6 +520,7 @@ int del_mtd_device(struct mtd_info *mtd)
 		device_unregister(&mtd->dev);
 
 		idr_remove(&mtd_idr, mtd->index);
+		of_node_put(mtd_get_of_node(mtd));
 
 		module_put(THIS_MODULE);
 		ret = 0;