nfsd/sunrpc: turn enqueueing a svc_xprt into a svc_serv operation

For now, all services use svc_xprt_do_enqueue, but once we add
workqueue-based service support, we'll need to do something different.

Signed-off-by: Shirley Ma <shirley.ma@oracle.com>
Acked-by: Jeff Layton <jlayton@primarydata.com>
Tested-by: Shirley Ma <shirley.ma@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfs/callback.c

@@ -309,6 +309,7 @@ err_bind:
 }
 
 static struct svc_serv_ops nfs_cb_sv_ops = {
+	.svo_enqueue_xprt	= svc_xprt_do_enqueue,
 };
 
 static struct svc_serv *nfs_callback_create_svc(int minorversion)