BatteryStats: update to use new notifyWakeup with wakeup reasons

As SystemSuspend support notifyWakeup callback with wakeup reason
embedded, BatteryStats no longer required to pull such reasons from
kernel files by itself.

Test: adb shell dumpsys batterystats --history
Bug: 171021049
Change-Id: I69717387586994b744297f5ac0f5b66ef2bdce32