qeth: avoid duplicate deletion of multicast addresses

if qeth_set_multicast_list() is performed on 2 CPUs in parallel,
card->ip_list may end corrupted.
Solution: In function __qeth_delete_all_mc()
          remove card->ip_list entry before invoking
          qeth_deregister_addr_entry(). Thus a 2nd invocation of
          qeth_set_multicast_list() cannot try to remove the
          same entry twice.

Signed-off-by Ursula Braun <braunu@de.ibm.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>

drivers/s390/net/qeth_main.c

@@ -823,14 +823,15 @@ __qeth_delete_all_mc(struct qeth_card *card, unsigned long *flags)
 again:
 	list_for_each_entry_safe(addr, tmp, &card->ip_list, entry) {
 		if (addr->is_multicast) {
+			list_del(&addr->entry);
 			spin_unlock_irqrestore(&card->ip_lock, *flags);
 			rc = qeth_deregister_addr_entry(card, addr);
 			spin_lock_irqsave(&card->ip_lock, *flags);
 			if (!rc) {
-				list_del(&addr->entry);
 				kfree(addr);
 				goto again;
-			}
+			} else
+				list_add(&addr->entry, &card->ip_list);
 		}
 	}
 }