perf_counters: account NMI interrupts

I noticed that kerneltop interrupts were accounted as NMI, but not their
perf counter origin.

Account NMI performance counter interrupts.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

 arch/x86/kernel/cpu/perf_counter.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)