Revert "workqueue: remove unused cancel_work()"

[ Upstream commit 73b4b53276a1d6290cd4f47dbbc885b6e6e59ac6 ]

This reverts commit 6417250d3f.

amdpgu need this function in order to prematurly stop pending
reset works when another reset work already in progress.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Lai Jiangshan<jiangshanlai@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Stable-dep-of: 91d3d149978b ("r8169: prevent potential deadlock in rtl8169_close")
Signed-off-by: Sasha Levin <sashal@kernel.org>

kernel/workqueue.c

@@ -3240,6 +3240,15 @@ 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);
+}
+EXPORT_SYMBOL(cancel_work);
+
 /**
  * cancel_delayed_work - cancel a delayed work
  * @dwork: delayed_work to cancel