workqueue: Use cond_resched_rcu_qs macro

Tidy up and use cond_resched_rcu_qs when calling cond_resched and
reporting potential quiescent state to RCU.  Splitting this change in
this way allows easy backporting to -stable for kernel versions not
having cond_resched_rcu_qs().
Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/workqueue.c

@@ -2046,8 +2046,7 @@ __acquires(&pool->lock)
 	 * stop_machine. At the same time, report a quiescent RCU state so
 	 * the same condition doesn't freeze RCU.
 	 */
-	rcu_note_voluntary_context_switch(current);
-	cond_resched();
+	cond_resched_rcu_qs();
 
 	spin_lock_irq(&pool->lock);