GCS_MAVLink: run a bit faster on serial ports with flow control

with flow control we can afford to push the radio a bit harder

libraries/GCS_MAVLink/GCS_Logs.cpp

@@ -136,6 +136,13 @@ void GCS_MAVLINK::handle_log_send(DataFlash_Class &dataflash)
     if (chan == MAVLINK_COMM_0 && hal.gpio->usb_connected()) {
         // when on USB we can send a lot more data
         num_sends = 40;
+    } else if (chan == MAVLINK_COMM_1 && 
+               hal.uartC->get_flow_control() != AP_HAL::UARTDriver::FLOW_CONTROL_DISABLE) {
+        num_sends = 10;        
+    } else if (chan == MAVLINK_COMM_2 && 
+               hal.uartD != NULL &&
+               hal.uartD->get_flow_control() != AP_HAL::UARTDriver::FLOW_CONTROL_DISABLE) {
+        num_sends = 10;        
     }
 
 #if CONFIG_HAL_BOARD == HAL_BOARD_AVR_SITL
@@ -143,10 +150,6 @@ void GCS_MAVLINK::handle_log_send(DataFlash_Class &dataflash)
     num_sends = 40;
 #endif
 
-    if (stream_slowdown != 0) {
-        // we're using a radio and starting to clag up, slowdown log send
-        num_sends = 1;
-    }
     for (uint8_t i=0; i<num_sends; i++) {
         if (_log_sending) {
             if (!handle_log_send_data(dataflash)) break;