emac_mii_writereg
mii->mii_writereg = emac_mii_writereg;
int emac_mii_writereg (device_t, int, int, uint16_t);
static int emac_mii_writereg(device_t, int, int, uint16_t);
mii->mii_writereg = emac_mii_writereg;