RT2560_TX_VALID
!(letoh32(desc->flags) & RT2560_TX_VALID))
desc->flags &= ~htole32(RT2560_TX_VALID);
htole32(RT2560_TX_BUSY | RT2560_TX_VALID);
desc->flags |= htole32(RT2560_TX_BUSY | RT2560_TX_VALID);
!(letoh32(desc->flags) & RT2560_TX_VALID))
desc->flags &= ~htole32(RT2560_TX_VALID);