xen: xenbus: use put_device() instead of kfree()

Never directly free @dev after calling device_register(), even
if it returned an error! Always use put_device() to give up the
reference initialized.
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Reviewed-by: NJuergen Gross <jgross@suse.com>
Signed-off-by: NJuergen Gross <jgross@suse.com>

drivers/xen/xenbus/xenbus_probe.c

@@ -466,8 +466,11 @@ int xenbus_probe_node(struct xen_bus_type *bus,
 
 	/* Register with generic device framework. */
 	err = device_register(&xendev->dev);
-	if (err)
+	if (err) {
+		put_device(&xendev->dev);
+		xendev = NULL;
 		goto fail;
+	}
 
 	return 0;
 fail: