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/bridge/netfilter/ebt_arp.c b/net/bridge/netfilter/ebt_arp.c
index 6203f4d..cd457b8 100644
--- a/net/bridge/netfilter/ebt_arp.c
+++ b/net/bridge/netfilter/ebt_arp.c
@@ -16,7 +16,7 @@
 #include <linux/netfilter_bridge/ebt_arp.h>
 
 static bool
-ebt_arp_mt(const struct sk_buff *skb, const struct xt_action_param *par)
+ebt_arp_mt(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	const struct ebt_arp_info *info = par->matchinfo;
 	const struct arphdr *ah;