workqueue: remove unused cancel_work()

Found this by accident.
There are no usages of bare cancel_work() in current kernel source.
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

include/linux/workqueue.h

@@ -456,7 +456,6 @@ extern int schedule_on_each_cpu(work_func_t func);
 int execute_in_process_context(work_func_t fn, struct execute_work *);
 
 extern bool flush_work(struct work_struct *work);
-extern bool cancel_work(struct work_struct *work);
 extern bool cancel_work_sync(struct work_struct *work);
 
 extern bool flush_delayed_work(struct delayed_work *dwork);

kernel/workqueue.c

@@ -3018,14 +3018,6 @@ static bool __cancel_work(struct work_struct *work, bool is_dwork)
 	return ret;
 }
 
-/*
- * See cancel_delayed_work()
- */
-bool cancel_work(struct work_struct *work)
-{
-	return __cancel_work(work, false);
-}
-
 /**
  * cancel_delayed_work - cancel a delayed work
  * @dwork: delayed_work to cancel