Merge branch 'axiennet-mdio-bus-freq'

Andy Chiu says:

====================
net: axienet: Use a DT property to configure frequency of the MDIO bus

Some FPGA platforms have to set frequency of the MDIO bus lower than 2.5
MHz. Thus, we use a DT property, which is "clock-frequency", to work
with it at boot time. The default 2.5 MHz would be set if the property
is not pressent. Also, factor out mdio enable/disable functions due to
the api change since 253761a0e61b7.

Changelog:
--- v5 ---
1. Make dt-binding patch prior to the implementation patch.
2. Disable mdio bus in error path.
3. Update description of some functions.
--- v4 ---
1. change MAX_MDIO_FREQ to DEFAULT_MDIO_FREQ as suggested by Andrew.
--- v3 RESEND ---
1. Repost the exact same patch again
--- v3 ---
1. Fix coding style, and make probing of the driver fail if MDC overflow
--- v2 ---
1. Use clock-frequency, as defined in mdio.yaml, to configure MDIO
   clock.
2. Only print out frequency if it is set to a non-standard value.
3. Reduce the scope of axienet_mdio_enable and remove
   axienet_mdio_disable because no one really uses it anymore.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>