perf_counter: frequency based adaptive irq_period, 32-bit fix

fix:

  kernel/built-in.o: In function `perf_counter_alloc':
  perf_counter.c:(.text+0x7ddc7): undefined reference to `__udivdi3'

[ Impact: build fix on 32-bit systems ]
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <1242394667.6642.1887.camel@laptop>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/perf_counter.c

@@ -2942,7 +2942,7 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
 
 	hwc = &counter->hw;
 	if (hw_event->freq && hw_event->irq_freq)
-		hwc->irq_period = TICK_NSEC / hw_event->irq_freq;
+		hwc->irq_period = div64_u64(TICK_NSEC, hw_event->irq_freq);
 	else
 		hwc->irq_period = hw_event->irq_period;