perf_events, x86: Remove spurious counter reset from x86_pmu_enable()

At enable time the counter might still have a ->idx pointing to
a previously occupied location that might now be taken by
another event. Resetting the counter at that location with data
from this event will destroy the other counter's count.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <20100127221122.261477183@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/perf_event.c

@@ -1762,9 +1762,6 @@ static int x86_pmu_enable(struct perf_event *event)
 	cpuc->n_events = n;
 	cpuc->n_added  = n - n0;
 
-	if (hwc->idx != -1)
-		x86_perf_event_set_period(event, hwc, hwc->idx);
-
 	return 0;
 }