SUNRPC: Add correct rcu_dereference annotation in rpc_clnt_set_transport

rpc_clnt_set_transport should use rcu_derefence_protected(), as it is
only safe to be called with the rpc_clnt::cl_lock held.

Cc: Chuck Lever <Chuck.Lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index f167d9c..759b78b 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -272,7 +272,8 @@
 	struct rpc_xprt *old;
 
 	spin_lock(&clnt->cl_lock);
-	old = clnt->cl_xprt;
+	old = rcu_dereference_protected(clnt->cl_xprt,
+			lockdep_is_held(&clnt->cl_lock));
 
 	if (!xprt_bound(xprt))
 		clnt->cl_autobind = 1;