AP_Compass: AK8963: remove fallback to timer thread

Now that the bus thread from the AuxiliaryBus is implemented we can
remove the fallback.

libraries/AP_Compass/AP_Compass_AK8963.cpp

@@ -167,11 +167,7 @@ bool AP_Compass_AK8963::init()
 
     bus_sem->give();
 
-    /* timer needs to be called every 10ms so set the freq_div to 10 */
-    if (!_bus->register_periodic_callback(10000, FUNCTOR_BIND_MEMBER(&AP_Compass_AK8963::_update, void))) {
-        // fallback to timer
-        hal.scheduler->register_timer_process(FUNCTOR_BIND_MEMBER(&AP_Compass_AK8963::_update_timer, void));
-    }
+    _bus->register_periodic_callback(10000, FUNCTOR_BIND_MEMBER(&AP_Compass_AK8963::_update, void));
 
     return true;
 
@@ -264,27 +260,6 @@ void AP_Compass_AK8963::_update()
     }
 }
 
-/*
-  update from timer callback
- */
-void AP_Compass_AK8963::_update_timer()
-{
-    uint32_t now = AP_HAL::micros();
-
-    if (now - _last_update_timestamp < 10000) {
-        return;
-    }
-
-    if (!_bus->get_semaphore()->take_nonblocking()) {
-        return;
-    }
-
-    _update();
-    _last_update_timestamp = now;
-
-    _bus->get_semaphore()->give();
-}
-
 bool AP_Compass_AK8963::_check_id()
 {
     for (int i = 0; i < 5; i++) {

libraries/AP_Compass/AP_Compass_AK8963.h

@@ -51,7 +51,6 @@ private:
     bool _calibrate();
 
     void _update();
-    void _update_timer();
 
     AP_AK8963_BusDriver *_bus;
 
@@ -60,7 +59,6 @@ private:
     float _mag_y_accum;
     float _mag_z_accum;
     uint32_t _accum_count;
-    uint32_t _last_update_timestamp;
 
     uint8_t _compass_instance;
     bool _initialized;