ArduPlane: avoid comparison between signed and unsigned

ArduPlane/Attitude.cpp

@@ -586,7 +586,7 @@ bool Plane::suppress_throttle(void)
 
         uint32_t launch_duration_ms = ((int32_t)g.takeoff_throttle_delay)*100 + 2000;
         if (is_flying() &&
-            millis() - started_flying_ms > MAX(launch_duration_ms,5000) && // been flying >5s in any mode
+            millis() - started_flying_ms > MAX(launch_duration_ms, 5000U) && // been flying >5s in any mode
             adjusted_relative_altitude_cm() > 500 && // are >5m above AGL/home
             labs(ahrs.pitch_sensor) < 3000 && // not high pitch, which happens when held before launch
             gps_movement) { // definate gps movement

ArduPlane/geofence.cpp

@@ -49,7 +49,7 @@ static const StorageAccess fence_storage(StorageManager::StorageFence);
  */
 uint8_t Plane::max_fencepoints(void)
 {
-    return MIN(255, fence_storage.size() / sizeof(Vector2l));
+    return MIN(255U, fence_storage.size() / sizeof(Vector2l));
 }
 
 /*