m68k: emu: Fix invalid free in nfeth_cleanup()

In the for loop all nfeth_dev array members should be freed, not only
the first one.  Freeing only the first array member can cause
double-free bugs and memory leaks.

Fixes: 9cd7b148 ("m68k/atari: ARAnyM - Add support for network access")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/20210705204727.10743-1-paskripkin@gmail.comSigned-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/emu/nfeth.c

@@ -254,8 +254,8 @@ static void __exit nfeth_cleanup(void)
 
 	for (i = 0; i < MAX_UNIT; i++) {
 		if (nfeth_dev[i]) {
-			unregister_netdev(nfeth_dev[0]);
-			free_netdev(nfeth_dev[0]);
+			unregister_netdev(nfeth_dev[i]);
+			free_netdev(nfeth_dev[i]);
 		}
 	}
 	free_irq(nfEtherIRQ, nfeth_interrupt);