APMrover2: implement HAL::Callbacks

Also removes includes for each board since they are not necessary
anymore.

APMrover2/APMrover2.cpp

@@ -505,16 +505,4 @@ void Rover::update_navigation()
     }
 }
 
-void setup(void);
-void loop(void);
-
-void setup(void)
-{
-    rover.setup();
-}
-void loop(void)
-{
-    rover.loop();
-}
-
-AP_HAL_MAIN();
+AP_HAL_MAIN_CALLBACKS(&rover);

APMrover2/Rover.h

@@ -73,13 +73,6 @@
 #include <AP_BoardConfig/AP_BoardConfig.h>
 #include <AP_Frsky_Telem/AP_Frsky_Telem.h>
 
-#include <AP_HAL_AVR/AP_HAL_AVR.h>
-#include <AP_HAL_SITL/AP_HAL_SITL.h>
-#include <AP_HAL_PX4/AP_HAL_PX4.h>
-#include <AP_HAL_VRBRAIN/AP_HAL_VRBRAIN.h>
-#include <AP_HAL_FLYMAPLE/AP_HAL_FLYMAPLE.h>
-#include <AP_HAL_Linux/AP_HAL_Linux.h>
-#include <AP_HAL_Empty/AP_HAL_Empty.h>
 #include "compat.h"
 
 #include <AP_Notify/AP_Notify.h>      // Notify library
@@ -97,16 +90,16 @@
 
 #include <AP_Declination/AP_Declination.h> // ArduPilot Mega Declination Helper Library
 
-class Rover {
+class Rover : public AP_HAL::HAL::Callbacks {
 public:
     friend class GCS_MAVLINK;
     friend class Parameters;
 
     Rover(void);
 
-    // public member functions
-    void setup(void);
-    void loop(void);
+    // HAL::Callbacks implementation.
+    void setup(void) override;
+    void loop(void) override;
 
 private:
     AP_HAL::BetterStream* cliSerial;