Merge branch 'net-axienet-dynamically-enable-mdio-interface'

Radhey Shyam Pandey says:

====================
net: axienet: Dynamically enable MDIO interface

This patchset dynamically enable MDIO interface. The background for this
change is coming from Cadence GEM controller(macb) in which MDC is active
only during MDIO read or write operations while the PHY registers are
read or written. It is implemented as an IP feature.

For axiethernet as dynamic MDC enable/disable is not supported in hw
we are implementing it in sw. This change doesn't affect any existing
functionality.
====================

Link: https://lore.kernel.org/r/1604402770-78045-1-git-send-email-radhey.shyam.pandey@xilinx.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>