net/fsl_pq_mdio: add support for the Fman 1G MDIO controller

The MDIO controller on the Frame Manager (Fman) is compatible with the
QE and Gianfar MDIO controllers, but we don't care about the TBI because
the Ethernet drivers (FMD) take care of programming it.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>