net: ethernet: aquantia: Fixes for aq_ndev_change_mtu

1)Removed unnecessary comparsion "old_mtu == new_mtu".
This check is not needed. Function aq_ndev_change_mtu wont be called
if mtu has not changed.

2)Removed extra assignment ndev->mtu = new_mtu;
This assignment already done inside __dev_set_mtu().

3)Use core MTU checking for min_mtu.
Signed-off-by: NPavel Belous <pavel.belous@aquantia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/aquantia/atlantic/aq_main.c

@@ -100,20 +100,10 @@ static int aq_ndev_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 static int aq_ndev_change_mtu(struct net_device *ndev, int new_mtu)
 {
 	struct aq_nic_s *aq_nic = netdev_priv(ndev);
-	int err = 0;
+	int err = aq_nic_set_mtu(aq_nic, new_mtu + ETH_HLEN);
 
-	if (new_mtu == ndev->mtu) {
-		err = 0;
-		goto err_exit;
-	}
-	if (new_mtu < 68) {
-		err = -EINVAL;
-		goto err_exit;
-	}
-	err = aq_nic_set_mtu(aq_nic, new_mtu + ETH_HLEN);
 	if (err < 0)
 		goto err_exit;
-	ndev->mtu = new_mtu;
 
 	if (netif_running(ndev)) {
 		aq_ndev_close(ndev);

drivers/net/ethernet/aquantia/atlantic/aq_nic.c

@@ -214,6 +214,7 @@ struct aq_nic_s *aq_nic_alloc_cold(const struct net_device_ops *ndev_ops,
 	SET_NETDEV_DEV(ndev, dev);
 
 	ndev->if_port = port;
+	ndev->min_mtu = ETH_MIN_MTU;
 	self->ndev = ndev;
 
 	self->aq_pci_func = aq_pci_func;