Make sure to drop the reference taken by of_phy_find_device() when
looking up a fixed-link phydev during probe.

Fixes: 57ba4c9b ("fsl/fman: Add FMan MAC support")
Signed-off-by: NJohan Hovold <johan@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>