xen-sysdev: Remove user_creatable flag

TYPE_XENSYSDEV is only used internally by xen_be_init(), and is
not supposed to be plugged/unplugged dynamically. Remove the
user_creatable flag from the device class.

Cc: Juergen Gross <jgross@suse.com>,
Cc: Peter Maydell <peter.maydell@linaro.org>,
Cc: Thomas Huth <thuth@redhat.com>
Cc: sstabellini@kernel.org
Cc: Markus Armbruster <armbru@redhat.com>,
Cc: Marcel Apfelbaum <marcel@redhat.com>,
Cc: Laszlo Ersek <lersek@redhat.com>
Acked-by: NJuergen Gross <jgross@suse.com>
Acked-by: NMarcel Apfelbaum <marcel@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Message-Id: <20170503203604.31462-21-ehabkost@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

hw/xen/xen_backend.c

@@ -664,11 +664,6 @@ static void xen_sysdev_class_init(ObjectClass *klass, void *data)
     k->init = xen_sysdev_init;
     dc->props = xen_sysdev_properties;
     dc->bus_type = TYPE_XENSYSBUS;
-    /*
-     * FIXME: Set only because we are not sure yet if this device
-     * will be outside the q35 sysbus whitelist.
-     */
-    dc->user_creatable = true;
 }
 
 static const TypeInfo xensysdev_info = {