kthread_work: remove the unused wait_queue_head

struct kthread_work {

	struct list_head	node;

	kthread_work_func_t	func;

	wait_queue_head_t	done;

	struct kthread_worker	*worker;

};

#define KTHREAD_WORK_INIT(work, fn)	{				\

	.node = LIST_HEAD_INIT((work).node),				\

	.func = (fn),							\

	.done = __WAIT_QUEUE_HEAD_INITIALIZER((work).done),		\

	}

#define DEFINE_KTHREAD_WORKER(worker)					\

	struct kthread_work work = KTHREAD_WORK_INIT(work, fn)

/*

 * kthread_worker.lock and kthread_work.done need their own lockdep class

 * keys if they are defined on stack with lockdep enabled.  Use the

 * following macros when defining them on stack.

 * kthread_worker.lock needs its own lockdep class key when defined on

 * stack with lockdep enabled.  Use the following macros in such cases.

 */

#ifdef CONFIG_LOCKDEP

# define KTHREAD_WORKER_INIT_ONSTACK(worker)				\

	({ init_kthread_worker(&worker); worker; })

# define DEFINE_KTHREAD_WORKER_ONSTACK(worker)				\

	struct kthread_worker worker = KTHREAD_WORKER_INIT_ONSTACK(worker)

# define KTHREAD_WORK_INIT_ONSTACK(work, fn)				\

	({ init_kthread_work((&work), fn); work; })

# define DEFINE_KTHREAD_WORK_ONSTACK(work, fn)				\

	struct kthread_work work = KTHREAD_WORK_INIT_ONSTACK(work, fn)

#else

# define DEFINE_KTHREAD_WORKER_ONSTACK(worker) DEFINE_KTHREAD_WORKER(worker)

# define DEFINE_KTHREAD_WORK_ONSTACK(work, fn) DEFINE_KTHREAD_WORK(work, fn)

#endif

extern void __init_kthread_worker(struct kthread_worker *worker,

		memset((work), 0, sizeof(struct kthread_work));		\

		INIT_LIST_HEAD(&(work)->node);				\

		(work)->func = (fn);					\

		init_waitqueue_head(&(work)->done);			\

	} while (0)

int kthread_worker_fn(void *worker_ptr);