AR5K_OFDM_NUM_BITS_PER_SYM
if (AR5K_OFDM_NUM_BITS_PER_SYM(rate->rateKbps) == 0)
howmany(AR5K_OFDM_NUM_BITS(_frmlen), AR5K_OFDM_NUM_BITS_PER_SYM(_kbps))