ex_mii_send_bits
ex_mii_send_bits(sc, 1, 2); /* start */
ex_mii_send_bits(sc, 2, 2); /* read command */
ex_mii_send_bits(sc, phy, 5);
ex_mii_send_bits(sc, reg, 5);
ex_mii_send_bits(sc, 1, 2); /* start */
ex_mii_send_bits(sc, 1, 2); /* write */
ex_mii_send_bits(sc, phy, 5);
ex_mii_send_bits(sc, reg, 5);
ex_mii_send_bits(sc, 2, 2); /* ack/turnaround */
ex_mii_send_bits(sc, data, 16);