message: add constant POLL_PERIOD
  define period to check, if the driver should still use the polling mode
diff: @@ -18,6 +18,9 @@ static NIC_QUEUE: SpinlockIrqSave<BTreeMap<usize, TaskHandle>> =
  SpinlockIrqSave::new(BTreeMap::new());
  static POLLING: AtomicBool = AtomicBool::new(false);
  +/// period (in usec) to check, if the driver should still use the polling mode
  +const POLL_PERIOD: u64 = 20_000;
  +
  /// set driver in polling mode and threads will not be blocked
  fn set_polling_mode(value: bool) {
  // is the driver already in polling mode?
  @@ -53,12 +56,12 @@ pub fn netwait_and_wakeup(handles: &[usize], millis: Option<u64>) {
  let mut reset_nic = false;
  - // every 20ms we check if the driver should be in the polling mode
  + // check if the driver should be in the polling mode
  while POLLING.swap(false, Ordering::SeqCst) == true {
  reset_nic = true;
  let core_scheduler = core_scheduler();
  - let wakeup_time = Some(crate::arch::processor::get_timer_ticks() + 20_000);
  + let wakeup_time = Some(crate::arch::processor::get_timer_ticks() + POLL_PERIOD);
  core_scheduler.block_current_task(wakeup_time);
  