netfilter: nf_conntrack_bridge: initialize err to 0

K2CI reported a problem:

	consume_skb(skb);
	return err;
[nf_br_ip_fragment() error]  uninitialized symbol 'err'.

err is not initialized, because returning 0 is expected, initialize err
to 0.

Fixes: 3c171f49 ("netfilter: bridge: add connection tracking system")
Reported-by: k2ci <kernel-bot@kylinos.cn>
Signed-off-by: Linkui Xiao <xiaolinkui@kylinos.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/bridge/netfilter/nf_conntrack_bridge.c

@@ -37,7 +37,7 @@ static int nf_br_ip_fragment(struct net *net, struct sock *sk,
 	ktime_t tstamp = skb->tstamp;
 	struct ip_frag_state state;
 	struct iphdr *iph;
-	int err;
+	int err = 0;
 
 	/* for offloaded checksums cleanup checksum before fragmentation */
 	if (skb->ip_summed == CHECKSUM_PARTIAL &&