rt2661_txtime
uint16_t rt2661_txtime(int, int, uint32_t);
dur = rt2661_txtime(RAL_ACK_SIZE, rate, ic->ic_flags) +
dur = rt2661_txtime(pktlen, rate, ic->ic_flags) +
rt2661_txtime(RAL_ACK_SIZE, ackrate, ic->ic_flags) +
dur += rt2661_txtime(RAL_CTS_SIZE, rt2661_ack_rate(ic,
dur = rt2661_txtime(RAL_ACK_SIZE, rt2661_ack_rate(ic, rate),