net: ethernet: ti: davinci_emac: fix fixed-link phydev and of-node leaks

Make sure to deregister and free any fixed-link PHY registered using
of_phy_register_fixed_link() on probe errors and on driver unbind.

Also remember to put the of-node reference on probe errors.

Fixes: 1bb6aa56 ("net: davinci_emac: Add support for fixed-link
PHY")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>