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: NTrond Myklebust <Trond.Myklebust@netapp.com>

net/sunrpc/clnt.c

@@ -272,7 +272,8 @@ static struct rpc_xprt *rpc_clnt_set_transport(struct rpc_clnt *clnt,
 	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;