netdev/phy/of: Add more methods for binding PHY devices to drivers.

Allow PHY drivers to supply their own device matching function
(match_phy_device()), or to be matched OF compatible properties.

PHYs following IEEE802.3 clause 45 have more than one device
identifier constants, which breaks the default device matching code.
Other 10G PHYs don't follow the standard manufacturer/device
identifier register layout standards, but they do use the standard
MDIO bus protocols for register access.  Both of these require
adjustments to the PHY driver to device matching code.

If the there is an of_node associated with such a PHY, we can match it
to its driver using the "compatible" properties, just as we do with
certain platform devices.  If the "compatible" property match fails,
first check if there is a driver supplied matching function, and if
not fall back to the existing identifier matching rules.

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