AP_BattMonitor: Make type() const

libraries/AP_BattMonitor/AP_BattMonitor.h

@@ -143,8 +143,8 @@ public:
     int8_t get_highest_failsafe_priority(void) const { return _highest_failsafe_priority; };
 
     /// get_type - returns battery monitor type
-    enum AP_BattMonitor_Params::BattMonitor_Type get_type() { return get_type(AP_BATT_PRIMARY_INSTANCE); }
-    enum AP_BattMonitor_Params::BattMonitor_Type get_type(uint8_t instance) { return _params[instance].type(); }
+    enum AP_BattMonitor_Params::BattMonitor_Type get_type() const { return get_type(AP_BATT_PRIMARY_INSTANCE); }
+    enum AP_BattMonitor_Params::BattMonitor_Type get_type(uint8_t instance) const { return _params[instance].type(); }
 
     /// set_monitoring - sets the monitor type (used for example sketch only)
     void set_monitoring(uint8_t instance, uint8_t mon) { _params[instance]._type.set(mon); }