sched/core: Remove dead statement in __schedule()

Remove an unnecessary assignment of variable not used any more.

( This has no runtime effects as GCC is smart enough to optimize
  this out. )

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
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/1455159578-17256-1-git-send-email-byungchul.park@lge.com


[ Edited the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>