net: mdiobus: Introduce fwnode_mdiobus_register_phy()

Introduce fwnode_mdiobus_register_phy() to register PHYs on the
mdiobus. From the compatible string, identify whether the PHY is
c45 and based on this create a PHY device instance which is
registered on the mdiobus.

Along with fwnode_mdiobus_register_phy() also introduce
fwnode_find_mii_timestamper() and fwnode_mdiobus_phy_device_register()
since they are needed.
While at it, also use the newly introduced fwnode operation in
of_mdiobus_phy_device_register().

Signed-off-by: Calvin Johnson <calvin.johnson@oss.nxp.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Acked-by: Grant Likely <grant.likely@arm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>