Since skb_checksum_help() has been moved to xfrm[46]_output(), we don't
need the sk_buff ** argument in x->type->output anymore.  This patch
reverts it to a sk_buff *.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@redhat.com>