net: phy: realtek: add support for RTL8211

In preparation of adding phylib support to the r8169 driver we need
PHY drivers for all chip-internal PHY types. Fortunately almost all
of them are either supported by the Realtek PHY driver already or work
with the genphy driver.
Still missing is support for the PHY of RTL8169s, it requires a quirk
to properly support 100Mbit-fixed mode. The quirk was copied from
r8169 driver which copied it from the vendor driver.
Based on the PHYID the internal PHY seems to be a RTL8211.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>