GCS_MAVLink: use a larger log send queue for Linux

often on UDP or TCP with more bandwidth

libraries/GCS_MAVLink/GCS_Logs.cpp

@@ -159,7 +159,11 @@ void GCS_MAVLINK::handle_log_send(DataFlash_Class &dataflash)
         // when on USB we can send a lot more data
         num_sends = 40;
     } else if (have_flow_control()) {
-        num_sends = 10;        
+#if CONFIG_HAL_BOARD == HAL_BOARD_LINUX
+        num_sends = 80;
+#else
+        num_sends = 10;
+#endif
     }
 
 #if CONFIG_HAL_BOARD == HAL_BOARD_SITL