net: designware: Switch back to mdio_alloc()

net: designware: Switch back to mdio_alloc()

Use mdio_alloc() again to allocate MDIO bus. This is possible
because all the miiphybb parameters and ops passing is handled in
at bb_miiphy_read()/bb_miiphy_write() level.

This also fixes previously missed bb_miiphy_free() in .remove
callback of this driver. which does not pose a problem anymore.

Fixes: cbb69c2fafcc ("net: designware: Allocate bb_miiphy using bb_miiphy_alloc() and fill in callbacks")
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Paul Barker <paul.barker.ct@bp.renesas.com>