Sub: no need to fabs() get_default_speed_down() as it does fabs already

ArduSub/GCS_Mavlink.cpp

@@ -576,7 +576,7 @@ void GCS_MAVLINK_Sub::handleMessage(const mavlink_message_t &msg)
             climb_rate_cms = (packet.thrust - 0.5f) * 2.0f * sub.wp_nav.get_default_speed_up();
         } else {
             // descend at up to WPNAV_SPEED_DN
-            climb_rate_cms = (packet.thrust - 0.5f) * 2.0f * fabsf(sub.wp_nav.get_default_speed_down());
+            climb_rate_cms = (packet.thrust - 0.5f) * 2.0f * sub.wp_nav.get_default_speed_down();
         }
         sub.guided_set_angle(Quaternion(packet.q[0],packet.q[1],packet.q[2],packet.q[3]), climb_rate_cms);
         break;

ArduSub/control_guided.cpp

@@ -481,7 +481,7 @@ void Sub::guided_angle_control_run()
     float yaw_in = wrap_180_cd(guided_angle_state.yaw_cd);
 
     // constrain climb rate
-    float climb_rate_cms = constrain_float(guided_angle_state.climb_rate_cms, -fabsf(wp_nav.get_default_speed_down()), wp_nav.get_default_speed_up());
+    float climb_rate_cms = constrain_float(guided_angle_state.climb_rate_cms, -wp_nav.get_default_speed_down(), wp_nav.get_default_speed_up());
 
     // check for timeout - set lean angles and climb rate to zero if no updates received for 3 seconds
     uint32_t tnow = AP_HAL::millis();