xenbus/frontend: register bus earlier

Impact: bugfix

Make sure the frontend bus is registered early, before
any drivers want to attach.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
[corresponds to 1d5df318f87f in git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/xenbus/xenbus_probe_frontend.c

@@ -278,8 +278,7 @@ static int __init xenbus_probe_frontend_init(void)
 
 	return 0;
 }
-
-module_init(xenbus_probe_frontend_init);
+subsys_initcall(xenbus_probe_frontend_init);
 
 #ifndef MODULE
 static int __init boot_wait_for_devices(void)