litex_liteeth: Fix a double free in the remove function

'netdev' is a managed resource allocated in the probe using
'devm_alloc_etherdev()'.
It must not be freed explicitly in the remove function.

Fixes: ee7da21ac4c3 ("net: Add driver for LiteX's LiteETH network interface")
Signed-off-by: Christophe JAILLET <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/litex/litex_liteeth.c

···
 	struct net_device *netdev = platform_get_drvdata(pdev);
 
 	unregister_netdev(netdev);
-	free_netdev(netdev);
 
 	return 0;
 }