PHY_CNTL2_FDX
val = PHY_CNTL2_AUTONEG | PHY_CNTL2_100M | PHY_CNTL2_FDX;
val = PHY_CNTL2_100M | PHY_CNTL2_FDX;
val = PHY_CNTL2_FDX;
new = old & ~((PHY_CNTL2_AUTONEG | PHY_CNTL2_100M | PHY_CNTL2_FDX)