net: dsa: felix: don't deinitialize unused ports

ocelot_init_port is called only if dsa_is_unused_port == false, however
ocelot_deinit_port is called unconditionally. This causes a warning in
the skb_queue_purge inside ocelot_deinit_port saying that the spin lock
protecting ocelot_port->tx_skbs was not initialized.

Fixes: e5fb512d ("net: mscc: ocelot: deinitialize only initialized ports")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>