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_dscp.c b/net/netfilter/xt_dscp.c
index 2133b50..64670fc 100644
--- a/net/netfilter/xt_dscp.c
+++ b/net/netfilter/xt_dscp.c
@@ -25,7 +25,7 @@
 MODULE_ALIAS("ip6t_tos");
 
 static bool
-dscp_mt(const struct sk_buff *skb, const struct xt_action_param *par)
+dscp_mt(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	const struct xt_dscp_info *info = par->matchinfo;
 	u_int8_t dscp = ipv4_get_dsfield(ip_hdr(skb)) >> XT_DSCP_SHIFT;
@@ -34,7 +34,7 @@
 }
 
 static bool
-dscp_mt6(const struct sk_buff *skb, const struct xt_action_param *par)
+dscp_mt6(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	const struct xt_dscp_info *info = par->matchinfo;
 	u_int8_t dscp = ipv6_get_dsfield(ipv6_hdr(skb)) >> XT_DSCP_SHIFT;
@@ -54,8 +54,7 @@
 	return 0;
 }
 
-static bool tos_mt(const struct sk_buff *skb,
-		   const struct xt_action_param *par)
+static bool tos_mt(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	const struct xt_tos_match_info *info = par->matchinfo;