workqueue: unexport work_cpu()

This function no longer has any external users.  Unexport it.  It will
be removed later on.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 2ffa240..fe0745f 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -449,6 +449,7 @@
 };
 
 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 @@
  * 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