net/fsl: Use [acpi|of]_mdiobus_register

Depending on the device node type, call the specific OF or ACPI
mdiobus_register function.

Note: For both ACPI and DT cases, endianness of MDIO controllers
need to be specified using the "little-endian" property.

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>