sched/core: Remove unnecessary initialization in sched_init()

init_idle() is called immediately after:

  current->sched_class = &fair_sched_class;

init_idle() sets:

  current->sched_class = &idle_sched_class;

First assignment is superfluous.
Signed-off-by: Cheng Chao <cs.os.kernel@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/1473819536-7398-1-git-send-email-cs.os.kernel@gmail.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/core.c

@@ -7557,11 +7557,6 @@ void __init sched_init(void)
 	atomic_inc(&init_mm.mm_count);
 	enter_lazy_tlb(&init_mm, current);
 
-	/*
-	 * During early bootup we pretend to be a normal task:
-	 */
-	current->sched_class = &fair_sched_class;
-
 	/*
 	 * Make us the idle thread. Technically, schedule() should not be
 	 * called from this thread, however somewhere below it might be,