net/phy: Add support for Realtek RTL8211F

RTL8211F has different register definitions from RTL8211E.
Specially it needs to enable TXDLY in case of RGMII.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>