schedcore: Remove duplicated init_task's preempt_notifiers init

init_task's preempt_notifiers is initialized twice:

1) sched_init()
   -> INIT_HLIST_HEAD(&init_task.preempt_notifiers)

2) sched_init()
   -> init_idle(current,) <--- current task is init_task at this time
    -> __sched_fork(,current)
     -> INIT_HLIST_HEAD(&p->preempt_notifiers)

I think the first one is unnecessary, so remove it.

Signed-off-by: seokhoon.yoon <iamyooon@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1471339568-5790-1-git-send-email-iamyooon@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/core.c

@@ -7554,10 +7554,6 @@ void __init sched_init(void)
 
 	set_load_weight(&init_task);
 
-#ifdef CONFIG_PREEMPT_NOTIFIERS
-	INIT_HLIST_HEAD(&init_task.preempt_notifiers);
-#endif
-
 	/*
 	 * The boot idle thread does lazy MMU switching as well:
 	 */