dpaa2-eth: unregister the netdev before disconnecting from the PHY

The netdev should be unregistered before we are disconnecting from the
MAC/PHY so that the dev_close callback is called and the PHY and the
phylink workqueues are actually stopped before we are disconnecting and
destroying the phylink instance.

Fixes: 71947923 ("dpaa2-eth: add MAC/PHY support through phylink")
Signed-off-by: Robert-Ionut Alexa <robert-ionut.alexa@nxp.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>