workqueue: move flush_scheduled_work() to workqueue.h

flush_scheduled_work() is just a simple call to flush_work().

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/workqueue.c

@@ -2958,36 +2958,6 @@ int schedule_on_each_cpu(work_func_t func)
 	return 0;
 }
 
-/**
- * flush_scheduled_work - ensure that any scheduled work has run to completion.
- *
- * Forces execution of the kernel-global workqueue and blocks until its
- * completion.
- *
- * Think twice before calling this function!  It's very easy to get into
- * trouble if you don't take great care.  Either of the following situations
- * will lead to deadlock:
- *
- *	One of the work items currently on the workqueue needs to acquire
- *	a lock held by your code or its caller.
- *
- *	Your code is running in the context of a work routine.
- *
- * They will be detected by lockdep when they occur, but the first might not
- * occur very often.  It depends on what work items are on the workqueue and
- * what locks they need, which you have no control over.
- *
- * In most situations flushing the entire workqueue is overkill; you merely
- * need to know that a particular work item isn't queued and isn't running.
- * In such cases you should use cancel_delayed_work_sync() or
- * cancel_work_sync() instead.
- */
-void flush_scheduled_work(void)
-{
-	flush_workqueue(system_wq);
-}
-EXPORT_SYMBOL(flush_scheduled_work);
-
 /**
  * execute_in_process_context - reliably execute the routine with user context
  * @fn:		the function to execute