message: release sem_usb_tx in usbd_cdc.c
diff: #include "usbd_cdc.h"
  #include "usbd_desc.h"
  #include "usbd_ctlreq.h"
  -
  +#include <cmsis_os.h>
  +#include <freertos_vars.h>
  /** @addtogroup STM32_USB_DEVICE_LIBRARY
  * @{
  @@ -669,7 +670,7 @@ static uint8_t USBD_CDC_DataIn (USBD_HandleTypeDef *pdev, uint8_t epnum)
  {
  hcdc->TxState = 0;
  -
  + osSemaphoreRelease(sem_usb_tx);
  return USBD_OK;
  }
  else
  