ipv6: frag: remove unused field

csum field in struct frag_queue is not used, remove it.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ipv6.h

@@ -603,7 +603,6 @@ struct frag_queue {
 	struct in6_addr		daddr;
 
 	int			iif;
-	unsigned int		csum;
 	__u16			nhoffset;
 	u8			ecn;
 };