net: phy: realtek: add missing entry for RTL8211C to mdio_device_id table

Add missing entry for RTL8211C to mdio_device_id table.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Fixes: cf87915c ("net: phy: realtek: add support for RTL8211C")
Signed-off-by: David S. Miller <davem@davemloft.net>