This patch allows to create PHYs from DT in case
if they are explicitly defined. The of_mdiobus_register() is
used for such purposes.

For backward compatibility, call  of_mdiobus_register() only in case
if at least one PHY's child is defined in DT, otherwise rollback to
mdiobus_register().
Reviewed-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: NMugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: NGrygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>