workqueue: Fix missing kfree(rescuer) in destroy_workqueue()

Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NQian Cai <cai@lca.pw>
Fixes: def98c84 ("workqueue: Fix spurious sanity check failures in destroy_workqueue()")

kernel/workqueue.c

@@ -4345,6 +4345,7 @@ void destroy_workqueue(struct workqueue_struct *wq)
 
 		/* rescuer will empty maydays list before exiting */
 		kthread_stop(rescuer->task);
+		kfree(rescuer);
 	}
 
 	/* sanity checks */