xenbus: convert bus code to use dev_groups

The dev_attrs field of struct bus_type is going away soon, dev_groups
should be used instead.  This converts the xenbus code to use the
correct field.

Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: <xen-devel@lists.xenproject.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/xen/xenbus/xenbus_probe_backend.c

@@ -200,7 +200,7 @@ static struct xen_bus_type xenbus_backend = {
 		.probe		= xenbus_dev_probe,
 		.remove		= xenbus_dev_remove,
 		.shutdown	= xenbus_dev_shutdown,
-		.dev_attrs	= xenbus_dev_attrs,
+		.dev_groups	= xenbus_dev_groups,
 	},
 };