netfilter: bridge: refactor frag_max_size

Currently frag_max_size is member of br_input_skb_cb and copied back and
forth using IPCB(skb) and BR_INPUT_SKB_CB(skb) each time it is changed or
used.

Attach frag_max_size to nf_bridge_info and set value in pre_routing and
forward functions. Use its value in forward and xmit functions.

Signed-off-by: Bernhard Thaler <bernhard.thaler@wvnet.at>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index f70fc0e..32b105e 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -174,6 +174,7 @@
 		BRNF_PROTO_PPPOE
 	} orig_proto:8;
 	bool			pkt_otherhost;
+	__u16			frag_max_size;
 	unsigned int		mask;
 	struct net_device	*physindev;
 	union {