net: davinci_mdio: reuse for keystone2 arch

The similar MDIO HW blocks is used by keystone 2 SoCs as
in Davinci SoCs:
- one in Gigabit Ethernet (GbE) Switch Subsystem
  See http://www.ti.com/lit/ug/sprugv9d/sprugv9d.pdf
- one in 10 Gigabit Ethernet Subsystem
  See http://www.ti.com/lit/ug/spruhj5/spruhj5.pdf



Hence, reuse Davinci MDIO driver for Keystone 2 and
enable TI networking for Keystone 2 devices

Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>