lantiq_etop: use free_netdev(netdev) instead of kfree()

Freeing netdev without free_netdev() leads to net, tx leaks.
And it may lead to dereferencing freed pointer.
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/lantiq_etop.c

@@ -769,7 +769,7 @@ ltq_etop_probe(struct platform_device *pdev)
 	return 0;
 
 err_free:
-	kfree(dev);
+	free_netdev(dev);
 err_out:
 	return err;
 }