r8169: Modify the method for setting firmware

Remove useless action PHY_READ_EFUSE, PHY_READ_MAC_BYTE, PHY_WRITE_MAC_BYTE,
PHY_WRITE_ERI_WORD. And define the new action PHY_MDIO_CHG.

PHY_MDIO_CHG is used to modify the mdio operation. By the way, the
firmware could support setting mac ocp.

Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>