Perf: Check perf activity on correct CPU

The CPU hotplug notifier is not always preempt safe.
So relying on smp_processor_id() is not correct.

Use the cpu id from the notifier as the target
CPU to check for perf activity before hotplug or power
collapse.

CRs-Fixed: 454688
Change-Id: I1a96b236904a2c8ae2f82bbceab4ca8a195395d1
Signed-off-by: Ashwin Chaugule <ashwinc@codeaurora.org>