Revert "ARM: 7556/1: perf: fix updated event period in response to PERF_EVENT_IOC_PERIOD"

This reverts commit 3581fe0ef3.

Fixes to the handling of PERF_EVENT_IOC_PERIOD in the core code mean
we no longer have to play this horrible game.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1385560479-11014-2-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/arm/kernel/perf_event.c

@@ -99,10 +99,6 @@ int armpmu_event_set_period(struct perf_event *event)
 	s64 period = hwc->sample_period;
 	int ret = 0;
 
-	/* The period may have been changed by PERF_EVENT_IOC_PERIOD */
-	if (unlikely(period != hwc->last_period))
-		left = period - (hwc->last_period - left);
-
 	if (unlikely(left <= -period)) {
 		left = period;
 		local64_set(&hwc->period_left, left);