timer: Remove redundant __setup_timer*() macros

With __init_timer*() now matching __setup_timer*(), remove the redundant
internal interface, clean up the resulting definitions and add more
documentation.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 8d11580..bff39fa 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -241,17 +241,17 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
 #define __INIT_DELAYED_WORK(_work, _func, _tflags)			\
 	do {								\
 		INIT_WORK(&(_work)->work, (_func));			\
-		__setup_timer(&(_work)->timer,				\
-			      (TIMER_FUNC_TYPE)delayed_work_timer_fn,	\
-			      (_tflags) | TIMER_IRQSAFE);		\
+		__init_timer(&(_work)->timer,				\
+			     delayed_work_timer_fn,			\
+			     (_tflags) | TIMER_IRQSAFE);		\
 	} while (0)
 
 #define __INIT_DELAYED_WORK_ONSTACK(_work, _func, _tflags)		\
 	do {								\
 		INIT_WORK_ONSTACK(&(_work)->work, (_func));		\
-		__setup_timer_on_stack(&(_work)->timer,			\
-				       (TIMER_FUNC_TYPE)delayed_work_timer_fn,\
-				       (_tflags) | TIMER_IRQSAFE);	\
+		__init_timer_on_stack(&(_work)->timer,			\
+				      delayed_work_timer_fn,		\
+				      (_tflags) | TIMER_IRQSAFE);	\
 	} while (0)
 
 #define INIT_DELAYED_WORK(_work, _func)					\