healthd: move charger executable to healthd charger mode

* Add healthd charger mode ops
* Check for executable invocation as "charger", set charger mode if so
* Incorporate charger executable as healthd charger mode

Change-Id: I4a44e7a4c3a65ae9be94491f7f498aa48d4f8a84
diff --git a/healthd/healthd.h b/healthd/healthd.h
index 6e5f5a7..fb9504a 100644
--- a/healthd/healthd.h
+++ b/healthd/healthd.h
@@ -82,6 +82,14 @@
 
 extern struct healthd_mode_ops *healthd_mode_ops;
 
+// Charger mode
+
+void healthd_mode_charger_init(struct healthd_config *config);
+int healthd_mode_charger_preparetowait(void);
+void healthd_mode_charger_heartbeat(void);
+void healthd_mode_charger_battery_update(
+    struct android::BatteryProperties *props);
+
 // The following are implemented in libhealthd_board to handle board-specific
 // behavior.
 //