of: mdio: Refactor of_mdiobus_register_phy()

commit ef0eaf98c1d2a286cb68dddf62eaa0228d1be157 from
git://source.codeaurora.org/external/qoriq/qoriq-components/linux



Refactor of_mdiobus_register_phy() to use fwnode_mdiobus_register_phy().
Also, remove the of_find_mii_timestamper() since the fwnode variant is
used instead.

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>
(cherry picked from commit da45d7fe80406fdd0d1bae20270df9e2320fc5e7)
Signed-off-by: Meng Li <Meng.Li@windriver.com>