qos: Execute notifier callbacks atomically

Allowing the pm_qos notifier callbacks to execute without holding
pm_qos_lock can cause the callbacks to misbehave, e.g. the cpuidle
callback could erroneously send more IPIs than necessary.

Fix this by executing the pm_qos callbacks while pm_qos_lock is held.

Change-Id: I5b9a4ce7986956a2bf49c71f2d26307fc1afe6f6
Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>