AP_BattMonitor: Add macros for Fuel options

Adds macros for FuelFlow, FuelLevel_PWM, and FuelLevel_Analog. The features are enabled on all 2MB boards.

libraries/AP_BattMonitor/AP_BattMonitor.cpp

@@ -286,17 +286,21 @@ AP_BattMonitor::init()
             case Type::Sum:
                 drivers[instance] = new AP_BattMonitor_Sum(*this, state[instance], _params[instance], instance);
                 break;
-#if AP_BATTMON_FUEL_ENABLE
+#if AP_BATTMON_FUELFLOW_ENABLE
             case Type::FuelFlow:
                 drivers[instance] = new AP_BattMonitor_FuelFlow(*this, state[instance], _params[instance]);
                 break;
+#endif // AP_BATTMON_FUELFLOW_ENABLE
+#if AP_BATTMON_FUELLEVEL_PWM_ENABLE
             case Type::FuelLevel_PWM:
                 drivers[instance] = new AP_BattMonitor_FuelLevel_PWM(*this, state[instance], _params[instance]);
                 break;
+#endif // AP_BATTMON_FUELLEVEL_PWM_ENABLE
+#if AP_BATTMON_FUELLEVEL_ANALOG_ENABLE
             case Type::FuelLevel_Analog:
                 drivers[instance] = new AP_BattMonitor_FuelLevel_Analog(*this, state[instance], _params[instance]);
                 break;
-#endif // AP_BATTMON_FUEL_ENABLE
+#endif // AP_BATTMON_FUELLEVEL_ANALOG_ENABLE
 #if HAL_GENERATOR_ENABLED
             case Type::GENERATOR_ELEC:
                 drivers[instance] = new AP_BattMonitor_Generator_Elec(*this, state[instance], _params[instance]);

libraries/AP_BattMonitor/AP_BattMonitor.h

@@ -31,8 +31,16 @@
 #define AP_BATTMON_SMBUS_ENABLE 1
 #endif
 
-#ifndef AP_BATTMON_FUEL_ENABLE
+#ifndef AP_BATTMON_FUELFLOW_ENABLE
-#define AP_BATTMON_FUEL_ENABLE 1
+#define AP_BATTMON_FUELFLOW_ENABLE (BOARD_FLASH_SIZE > 1024)
+#endif
+
+#ifndef AP_BATTMON_FUELLEVEL_PWM_ENABLE
+#define AP_BATTMON_FUELLEVEL_PWM_ENABLE (BOARD_FLASH_SIZE > 1024)
+#endif
+
+#ifndef AP_BATTMON_FUELLEVEL_ANALOG_ENABLE
+#define AP_BATTMON_FUELLEVEL_ANALOG_ENABLE (BOARD_FLASH_SIZE > 1024)
 #endif
 
 // declare backend class