AP_BattMonitor: remove Bebop fixed capacity

Bebop, Bebop2 and Disco all use this class but it was always setting the capacity to the Bebop one, overriding the parameter

libraries/AP_BattMonitor/AP_BattMonitor_Backend.cpp

@@ -45,3 +45,9 @@ void AP_BattMonitor_Backend::set_capacity(uint32_t capacity)
 {
     _mon._pack_capacity[_instance] = capacity;
 }
+
+/// get capacity for this instance
+int32_t AP_BattMonitor_Backend::get_capacity() const
+{
+    return _mon.pack_capacity_mah(_instance);
+}

libraries/AP_BattMonitor/AP_BattMonitor_Backend.h

@@ -39,6 +39,9 @@ public:
 
     /// set capacity for this instance
     void set_capacity(uint32_t capacity);
+    
+    /// get capacity for this instance
+    int32_t get_capacity() const;
 
 protected:
     AP_BattMonitor                      &_mon;      // reference to front-end

libraries/AP_BattMonitor/AP_BattMonitor_Bebop.cpp

@@ -23,7 +23,6 @@
 #include <AP_HAL_Linux/RCOutput_Bebop.h>
 #include <AP_HAL_Linux/RCOutput_Disco.h>
 
-#define BATTERY_CAPACITY (1200U) /* mAh */
 #define BATTERY_VOLTAGE_COMPENSATION_LANDED (0.2f)
 
 
@@ -81,7 +80,6 @@ static const struct {
       
 void AP_BattMonitor_Bebop::init(void)
 {
-    set_capacity(BATTERY_CAPACITY);
     _battery_voltage_max = bat_lut[BATTERY_PERCENT_LUT_SIZE - 1].voltage;
     _prev_vbat_raw = bat_lut[BATTERY_PERCENT_LUT_SIZE - 1].voltage;
     _prev_vbat = bat_lut[BATTERY_PERCENT_LUT_SIZE - 1].voltage;
@@ -163,7 +161,7 @@ void AP_BattMonitor_Bebop::read(void)
     int ret;
     uint32_t tnow;
     BebopBLDC_ObsData data;
-    float remaining, vbat, vbat_raw;
+    float capacity, remaining, vbat, vbat_raw;
 
 #if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BEBOP
     auto rcout = Linux::RCOutput_Bebop::from(hal.rcout);
@@ -208,15 +206,15 @@ void AP_BattMonitor_Bebop::read(void)
         _battery_voltage_max = vbat;
     }
 
-    /* compute remaining battery percent */
+    /* compute remaining battery percent and get battery capacity */
     remaining = _compute_battery_percentage(vbat);
+    capacity = (float) get_capacity();
 
     /* fillup battery state */
     _state.voltage = vbat;
     _state.last_time_micros = tnow;
     _state.healthy = true;
-    _state.current_total_mah = BATTERY_CAPACITY -
-                (remaining * BATTERY_CAPACITY) / 100.0f;
+    _state.current_total_mah = capacity - (remaining * capacity) / 100.0f;
 }
 
 #endif