MHU_INTR_STAT
reg = bus_read_4(sc->res[0], MHU_CHAN_RX_HP + MHU_INTR_STAT);
reg = bus_read_4(sc->res[0], offset + MHU_INTR_STAT);
reg = bus_read_4(sc->res[0], MHU_CHAN_RX_LP + MHU_INTR_STAT);