AP_InertialSensor: remove unused get_last_sample_time_micros()

libraries/AP_InertialSensor/AP_InertialSensor_Flymaple.cpp

@@ -227,11 +227,6 @@ float AP_InertialSensor_Flymaple::get_delta_time(void)
     return _delta_time;
 }
 
-uint32_t AP_InertialSensor_Flymaple::get_last_sample_time_micros(void) 
-{
-    return _last_update_usec;
-}
-
 float AP_InertialSensor_Flymaple::get_gyro_drift_rate(void) 
 {
     // Dont really know this for the ITG-3200.

libraries/AP_InertialSensor/AP_InertialSensor_Flymaple.h

@@ -20,7 +20,6 @@ public:
     /* Concrete implementation of AP_InertialSensor functions: */
     bool            update();
     float        	get_delta_time();
-    uint32_t        get_last_sample_time_micros();
     float           get_gyro_drift_rate();
     bool            sample_available();
     bool            wait_for_sample(uint16_t timeout_ms);

libraries/AP_InertialSensor/AP_InertialSensor_HIL.cpp

@@ -37,9 +37,7 @@ bool AP_InertialSensor_HIL::update( void ) {
 float AP_InertialSensor_HIL::get_delta_time() {
     return _delta_time_usec * 1.0e-6;
 }
-uint32_t AP_InertialSensor_HIL::get_last_sample_time_micros() {
-    return _last_update_ms * 1000;
-}
+
 float AP_InertialSensor_HIL::get_gyro_drift_rate(void) {
     // 0.5 degrees/second/minute
     return ToRad(0.5/60);

libraries/AP_InertialSensor/AP_InertialSensor_HIL.h

@@ -15,7 +15,6 @@ public:
     /* Concrete implementation of AP_InertialSensor functions: */
     bool            update();
     float	        get_delta_time();
-    uint32_t        get_last_sample_time_micros();
     float           get_gyro_drift_rate();
     bool            sample_available();
     bool            wait_for_sample(uint16_t timeout_ms);

libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.h

@@ -18,7 +18,6 @@ public:
     /* Concrete implementation of AP_InertialSensor functions: */
     bool            update();
     float        	get_delta_time();    // get_delta_time returns the time period in seconds overwhich the sensor data was collected    
-    //uint32_t        get_last_sample_time_micros();  // last_sample_time - get time (in microseconds) that last sample was captured
     float           get_gyro_drift_rate();
 
     // sample_available() - true when a new sample is available