Rover: use abs for int within calc_speed_nudge

same issue resoled for log-write-nav-tuning

APMrover2/Log.cpp

@@ -130,8 +130,8 @@ void Rover::Log_Write_Nav_Tuning()
         time_us             : AP_HAL::micros64(),
         yaw                 : static_cast<uint16_t>(ahrs.yaw_sensor),
         wp_distance         : control_mode->get_distance_to_destination(),
-        target_bearing_cd   : static_cast<uint16_t>(fabsf(nav_controller->target_bearing_cd())),
-        nav_bearing_cd      : static_cast<uint16_t>(fabsf(nav_controller->nav_bearing_cd())),
+        target_bearing_cd   : static_cast<uint16_t>(abs(nav_controller->target_bearing_cd())),
+        nav_bearing_cd      : static_cast<uint16_t>(abs(nav_controller->nav_bearing_cd())),
         throttle            : int8_t(SRV_Channels::get_output_scaled(SRV_Channel::k_throttle)),
         xtrack_error        : nav_controller->crosstrack_error()
     };

APMrover2/mode.cpp

@@ -140,7 +140,7 @@ float Mode::calc_speed_nudge(float target_speed, float cruise_speed, float cruis
     }
 
     const float speed_increase_max = vehicle_speed_max - fabsf(target_speed);
-    float speed_nudge = ((fabsf(pilot_throttle) - 50.0f) / 50.0f) * speed_increase_max;
+    float speed_nudge = ((static_cast<float>(abs(pilot_throttle)) - 50.0f) * 0.02f) * speed_increase_max;
     if (pilot_throttle < 0) {
         speed_nudge = -speed_nudge;
     }