softlockup: fix false positives on CONFIG_NOHZ

David Miller reported soft lockup false-positives that trigger
on NOHZ due to CPUs idling for more than 10 seconds.

The solution is touch the softlockup watchdog when we return from
idle. (by definition we are not 'locked up' when we were idle)

 http://bugzilla.kernel.org/show_bug.cgi?id=9409Reported-by: NDavid Miller <davem@davemloft.net>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/time/tick-sched.c

@@ -133,6 +133,8 @@ void tick_nohz_update_jiffies(void)
 	if (!ts->tick_stopped)
 		return;
 
+	touch_softlockup_watchdog();
+
 	cpu_clear(cpu, nohz_cpu_mask);
 	now = ktime_get();