ENET_TXD_READY
if (txd->fd_status & ENET_TXD_READY)
while ((sc->sc_txdesc[idx].fd_status & ENET_TXD_READY) == 0) {
txd->fd_status |= ENET_TXD_READY;
txd_start->fd_status |= ENET_TXD_READY;