rcu: Remove comment referring to __stop_machine()

Although it used to be that CPU_DYING notifiers executed on the outgoing
CPU with interrupts disabled and with all other CPUs spinning, this is
no longer the case.  This commit therefore removes this obsolete comment.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcutree.c

@@ -2931,11 +2931,6 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
 		break;
 	case CPU_DYING:
 	case CPU_DYING_FROZEN:
-		/*
-		 * The whole machine is "stopped" except this CPU, so we can
-		 * touch any data without introducing corruption. We send the
-		 * dying CPU's callbacks to an arbitrarily chosen online CPU.
-		 */
 		for_each_rcu_flavor(rsp)
 			rcu_cleanup_dying_cpu(rsp);
 		rcu_cleanup_after_idle(cpu);