workqueue: unexport work_cpu()

This function no longer has any external users.  Unexport it.  It will
be removed later on.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NLai Jiangshan <laijs@cn.fujitsu.com>

include/linux/workqueue.h

@@ -426,7 +426,6 @@ extern bool cancel_delayed_work_sync(struct delayed_work *dwork);
 extern void workqueue_set_max_active(struct workqueue_struct *wq,
 				     int max_active);
 extern bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq);
-extern unsigned int work_cpu(struct work_struct *work);
 extern unsigned int work_busy(struct work_struct *work);
 
 /*

kernel/workqueue.c

@@ -449,6 +449,7 @@ static atomic_t unbound_pool_nr_running[NR_WORKER_POOLS] = {
 };
 
 static int worker_thread(void *__worker);
+static unsigned int work_cpu(struct work_struct *work);
 
 static int worker_pool_pri(struct worker_pool *pool)
 {
@@ -3419,13 +3420,12 @@ EXPORT_SYMBOL_GPL(workqueue_congested);
  * RETURNS:
  * CPU number if @work was ever queued.  WORK_CPU_NONE otherwise.
  */
-unsigned int work_cpu(struct work_struct *work)
+static unsigned int work_cpu(struct work_struct *work)
 {
 	struct global_cwq *gcwq = get_work_gcwq(work);
 
 	return gcwq ? gcwq->cpu : WORK_CPU_NONE;
 }
-EXPORT_SYMBOL_GPL(work_cpu);
 
 /**
  * work_busy - test whether a work is currently pending or running