batman-adv: Fix multicast packet loss with a single WANT_ALL_IPV4/6 flag

As the kernel doc describes too the code is supposed to skip adding
multicast TT entries if both the WANT_ALL_IPV4 and WANT_ALL_IPV6 flags
are present.

Unfortunately, the current code even skips adding multicast TT entries
if only either the WANT_ALL_IPV4 or WANT_ALL_IPV6 is present.

This could lead to IPv6 multicast packet loss if only an IGMP but not an
MLD querier is present for instance or vice versa.

Fixes: 687937ab ("batman-adv: Add multicast optimization support for bridged setups")
Signed-off-by: NLinus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: NSven Eckelmann <sven@narfation.org>
Signed-off-by: NSimon Wunderlich <sw@simonwunderlich.de>

net/batman-adv/multicast.c

@@ -543,8 +543,8 @@ static bool batadv_mcast_mla_tvlv_update(struct batadv_priv *bat_priv)
 		bat_priv->mcast.enabled = true;
 	}
 
-	return !(mcast_data.flags &
-		 (BATADV_MCAST_WANT_ALL_IPV4 | BATADV_MCAST_WANT_ALL_IPV6));
+	return !(mcast_data.flags & BATADV_MCAST_WANT_ALL_IPV4 &&
+		 mcast_data.flags & BATADV_MCAST_WANT_ALL_IPV6);
 }
 
 /**