UNIMAC_COMMAND_CONFIG
KASSERT((bcmeth_read_4(sc, UNIMAC_COMMAND_CONFIG) & TX_ENA) == 0);
bcmeth_write_4(sc, UNIMAC_COMMAND_CONFIG, sc->sc_cmdcfg);
bcmeth_write_4(sc, UNIMAC_COMMAND_CONFIG, SW_RESET);
bcmeth_write_4(sc, UNIMAC_COMMAND_CONFIG, 0);