rcu: Irq nesting is always 0 on rcu_enter_idle_common

Because tasks don't nest, the ->dyntick_nesting must always be zero upon
entry to rcu_idle_enter_common().  Therefore, pass "0" rather than the
counter itself.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcutree.c

@@ -350,12 +350,11 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
  */
 static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
 {
-	trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting);
+	trace_rcu_dyntick("Start", oldval, 0);
 	if (!is_idle_task(current)) {
 		struct task_struct *idle = idle_task(smp_processor_id());
 
-		trace_rcu_dyntick("Error on entry: not idle task",
-				   oldval, rdtp->dynticks_nesting);
+		trace_rcu_dyntick("Error on entry: not idle task", oldval, 0);
 		ftrace_dump(DUMP_ALL);
 		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
 			  current->pid, current->comm,