mtd: powernv_flash: set of_node in mtd's dev

This enables some features implemented in mtd subsystem like reading
label and partitioning info from DT.

Reported-by: Timothy Pearson <tpearson@raptorengineering.com>
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>

drivers/mtd/devices/powernv_flash.c

@@ -223,6 +223,7 @@ static int powernv_flash_set_driver_info(struct device *dev,
 	mtd->_read = powernv_flash_read;
 	mtd->_write = powernv_flash_write;
 	mtd->dev.parent = dev;
+	mtd_set_of_node(mtd, dev->of_node);
 	return 0;
 }