BatteryService: Add support for oem fast charger detection

Allows to indicate, whether a device is charged using a
proprietary oem fast charge solution, which write their status
to sysfs.

The oem fast charge detection tries to be as generic as possible and is
configured via overlays.

Path to sysfs to read status
  - core/res/res/values/ev_config.xml
    - config_oemFastChargerStatusPath
Value expected from read status (Defaults to "1" if not specified)
  - core/res/res/values/ev_config.xml
    - config_oemFastChargerStatusValue

Change-Id: I6f3598a5a6a3efc76553261d2cf73094170d4110
Signed-off-by: Joey Huab <joey@evolution-x.org>
5 files changed