Repair the Transmit mailbox (0,1,2) empty interrupt Flag not clear BUG

Author: samos2011

targets/TARGET_STM/TARGET_STM32F1/can_api.c

@@ -377,6 +377,15 @@ static void can_irq(CANName name, int id)
         tmp1 = __HAL_CAN_TRANSMIT_STATUS(&CanHandle, CAN_TXMAILBOX_0);
         tmp2 = __HAL_CAN_TRANSMIT_STATUS(&CanHandle, CAN_TXMAILBOX_1);
         tmp3 = __HAL_CAN_TRANSMIT_STATUS(&CanHandle, CAN_TXMAILBOX_2);
+        if (tmp1){
+            CanHandle.Instance->TSR |= CAN_TSR_RQCP0;
+        }
+        if (tmp2){
+            CanHandle.Instance->TSR |= CAN_TSR_RQCP1;
+        }
+        if (tmp3){
+            CanHandle.Instance->TSR |= CAN_TSR_RQCP2;
+        }
         if(tmp1 || tmp2 || tmp3)  
         {
             irq_handler(can_irq_ids[id], IRQ_TX);