net: phy: Add mdi(x) support in Microsemi PHYs driver

To connect two ports of the same configuration (MDI to MDI or
MDI-X to MDI-X) with a 10/100/1000 Mbit/s connection, an
Ethernet crossover cable is needed to cross over the transmit
and receive signals in the cable, so that they are matched at
the connector level.
When connecting an MDI port to an MDI-X port a straight through
cable is used while to connect two MDI ports or two MDI-X ports
a crossover cable must be used. Conventionally MDI is used on end
devices while MDI-X is used on hubs and switches

Auto MDI-X automatically detects the required cable connection
type and configures the connection appropriately, removing the
need for crossover cables to interconnect switches or connecting
PCs peer-to-peer.

Signed-off-by: Raju Lakkaraju <Raju.Lakkaraju@microsemi.com>
Signed-off-by: David S. Miller <davem@davemloft.net>