netdev/phy/of: Handle IEEE802.3 clause 45 Ethernet PHYs in of_mdiobus_register()

Define two new "compatible" values for Ethernet
PHYs. "ethernet-phy-ieee802.3-c22" and "ethernet-phy-ieee802.3-c45"
are used to indicate a PHY uses the corresponding protocol.

If a PHY is "compatible" with "ethernet-phy-ieee802.3-c45", we
indicate this so that get_phy_device() can properly probe the device.

If get_phy_device() fails, it was probably due to failing the probe of
the PHY identifier registers.  Since we have the device tree telling
us the PHY exists, go ahead and add it anyhow with a phy_id of zero.
There may be a driver match based on the "compatible" property.

Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>