Merge branch 'enetc-Add-mdio-support-and-device-tree-nodes'

Claudiu Manoil says:

====================
enetc: Add mdio support and device tree nodes

This is the missing part to enable PCI probing of the ENETC ethernet
ports on the LS1028A SoC and external traffic on the LS1028A RDB board.
It's one of the first items on the TODO list for the recently merged
ENETC ethernet driver.

v3: Add DT bindings doc for ENETC connections
v4: none
====================

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