net: mvneta: fix mtu change on port without link

It is incorrect to enable TX/RX queues (call by mvneta_port_up()) for
port without link. Indeed MTU change for interface without link causes TX
queues to stuck.

Fixes: c5aff182 ("net: mvneta: driver for Marvell Armada 370/XP
network unit")
Signed-off-by: Yelena Krivosheev <yelena@marvell.com>
[gregory.clement: adding Fixes tags and rewording commit log]
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mvneta.c

@@ -3196,7 +3196,6 @@ static int mvneta_change_mtu(struct net_device *dev, int mtu)
 
 	on_each_cpu(mvneta_percpu_enable, pp, true);
 	mvneta_start_dev(pp);
-	mvneta_port_up(pp);
 
 	netdev_update_features(dev);