libbatteryservice: Add average current property

Change-Id: I519c2fb9f7cec21d9f87e73fa96b2f58a7ab27a5
diff --git a/include/batteryservice/BatteryService.h b/include/batteryservice/BatteryService.h
index 6bc3f07..d141216 100644
--- a/include/batteryservice/BatteryService.h
+++ b/include/batteryservice/BatteryService.h
@@ -47,6 +47,7 @@
 enum {
     BATTERY_PROP_CHARGE_COUNTER = 1, // equals BatteryProperty.BATTERY_PROP_CHARGE_COUNTER constant
     BATTERY_PROP_CURRENT_NOW = 2, // equals BatteryProperty.BATTERY_PROP_CURRENT_NOW constant
+    BATTERY_PROP_CURRENT_AVG = 3, // equals BatteryProperty.BATTERY_PROP_CURRENT_AVG constant
 };
 
 struct BatteryProperties {