netfilter: xtables: deconstify struct xt_action_param for matches

In future, layer-3 matches will be an xt module of their own, and
need to set the fragoff and thoff fields. Adding more pointers would
needlessy increase memory requirements (esp. so for 64-bit, where
pointers are wider).

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
diff --git a/net/netfilter/xt_connlimit.c b/net/netfilter/xt_connlimit.c
index 6eec191..f130fd9 100644
--- a/net/netfilter/xt_connlimit.c
+++ b/net/netfilter/xt_connlimit.c
@@ -173,7 +173,7 @@
 }
 
 static bool
-connlimit_mt(const struct sk_buff *skb, const struct xt_action_param *par)
+connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	struct net *net = dev_net(par->in ? par->in : par->out);
 	const struct xt_connlimit_info *info = par->matchinfo;