sched/idle: Add deferrable vmstat_updater back

Deferrable vmstat_updater was missing in commit:

  c1de45ca ("sched/idle: Add support for tasks that inject idle")

Add it back.
Signed-off-by: NAubrey Li <aubrey.li@linux.intel.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Aubrey Li <aubrey.li@intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1496803742-38274-1-git-send-email-aubrey.li@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

kernel/sched/idle.c

@@ -219,6 +219,7 @@ static void do_idle(void)
 	 */
 
 	__current_set_polling();
+	quiet_vmstat();
 	tick_nohz_idle_enter();
 
 	while (!need_resched()) {