SSCOM_UTRSTAT
uart_setreg(bas, SSCOM_UTRSTAT, 0);
utrstat = bus_space_read_4(bas->bst, bas->bsh, SSCOM_UTRSTAT);
SSCOM_UTRSTAT);
bus_space_write_4(sc->sc_bas.bst, sc->sc_bas.bsh, SSCOM_UTRSTAT,