perf_event: x86: Optimize x86_pmu_disable()

x86_pmu_disable() removes the event from the cpuc->event_list[], however
since an event can only be on that list once, stop looking after we found
it.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/perf_event.c

@@ -1884,6 +1884,7 @@ static void x86_pmu_disable(struct perf_event *event)
 				cpuc->event_list[i-1] = cpuc->event_list[i];
 
 			--cpuc->n_events;
+			break;
 		}
 	}
 	perf_event_update_userpage(event);