AP_AHRS: remove groundspeed method from AHRS backend

if we want backends to be able to return this number as determined by a separate calculation (wheel odometry?) we can put it in the results object.  For now, just derive it from the groundspeed vector

Author: peterbarker

libraries/AP_AHRS/AP_AHRS.cpp

@@ -1420,28 +1420,6 @@ Vector2f AP_AHRS::_groundspeed_vector(void)
 
 float AP_AHRS::_groundspeed(void)
 {
-    switch (active_EKF_type()) {
-#if AP_AHRS_DCM_ENABLED
-    case EKFType::DCM:
-        return dcm.groundspeed();
-#endif
-#if HAL_NAVEKF2_AVAILABLE
-    case EKFType::TWO:
-#endif
-
-#if HAL_NAVEKF3_AVAILABLE
-    case EKFType::THREE:
-#endif
-
-#if AP_AHRS_EXTERNAL_ENABLED
-    case EKFType::EXTERNAL:
-#endif
-
-#if AP_AHRS_SIM_ENABLED
-    case EKFType::SIM:
-#endif
-        break;
-    }
     return groundspeed_vector().length();
 }
 

libraries/AP_AHRS/AP_AHRS_Backend.h

@@ -206,11 +206,6 @@ class AP_AHRS_Backend
         return false;
     }
 
-    // return ground speed estimate in meters/second. Used by ground vehicles.
-    float groundspeed(void) {
-        return groundspeed_vector().length();
-    }
-
     // return true if we will use compass for yaw
     virtual bool use_compass(void) = 0;