bridge: fix forwarding of IPv6

The commit 6b1e960f
    bridge: Reset IPCB when entering IP stack on NF_FORWARD
broke forwarding of IPV6 packets in bridge because it would
call bp_parse_ip_options with an IPV6 packet.
Reported-by: NNoah Meyerhans <noahm@debian.org>
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Reviewed-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/bridge/br_netfilter.c

@@ -737,7 +737,7 @@ static unsigned int br_nf_forward_ip(unsigned int hook, struct sk_buff *skb,
 		nf_bridge->mask |= BRNF_PKT_TYPE;
 	}
 
-	if (br_parse_ip_options(skb))
+	if (pf == PF_INET && br_parse_ip_options(skb))
 		return NF_DROP;
 
 	/* The physdev module checks on this */