iavf: Add change MTU message

Add a netdev_dbg log entry in case of a change of MTU so that user is
notified about this change in the same manner as in case of pf driver.
Signed-off-by: Patryk Małek <patryk.malek@intel.com>
Tested-by: George Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/iavf/iavf_main.c

@@ -3428,6 +3428,8 @@ static int iavf_change_mtu(struct net_device *netdev, int new_mtu)
 {
 	struct iavf_adapter *adapter = netdev_priv(netdev);
 
+	netdev_dbg(netdev, "changing MTU from %d to %d\n",
+		   netdev->mtu, new_mtu);
 	netdev->mtu = new_mtu;
 	if (CLIENT_ENABLED(adapter)) {
 		iavf_notify_client_l2_params(&adapter->vsi);