s390/irq: count cpu restart events

Count CPU Restart events and make them visible via /proc/interrupts.
Every CPU hotplug (online) event will increase the per cpu counter.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/smp.c

@@ -709,6 +709,7 @@ static void __cpuinit smp_start_secondary(void *cpuvoid)
 	pfault_init();
 	notify_cpu_starting(smp_processor_id());
 	set_cpu_online(smp_processor_id(), true);
+	inc_irq_stat(CPU_RST);
 	local_irq_enable();
 	/* cpu_idle will call schedule for us */
 	cpu_idle();