rcu: Enable stall warnings for synchronize_rcu_expedited()

This commit redirects synchronize_rcu_expedited()'s wait to
synchronize_sched_expedited_wait(), thus enabling RCU CPU
stall warnings.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/tree_plugin.h

@@ -761,8 +761,7 @@ void synchronize_rcu_expedited(void)
 
 	/* Wait for snapshotted ->blkd_tasks lists to drain. */
 	rnp = rcu_get_root(rsp);
-	wait_event(rsp->expedited_wq,
-		   sync_rcu_preempt_exp_done(rnp));
+	synchronize_sched_expedited_wait(rsp);
 
 	/* Clean up and exit. */
 	rcu_exp_gp_seq_end(rsp);