power: Add 1.0 HAL for devices that don't have WiFi stats

Some devices (cough Broadcom cough) don't have nodes that return WiFi
stats, so add a 1.0 HAL that devices can build. Also actually enable
the system power stats code and use it. Also add a legacy stats option
for devices that use an old RPM driver

Change-Id: If946b81b589ce11b0bde46437396bb4be74a731a
7 files changed