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_physdev.c b/net/netfilter/xt_physdev.c
index 298cd29..d7ca16b 100644
--- a/net/netfilter/xt_physdev.c
+++ b/net/netfilter/xt_physdev.c
@@ -22,7 +22,7 @@
 
 
 static bool
-physdev_mt(const struct sk_buff *skb, const struct xt_action_param *par)
+physdev_mt(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	static const char nulldevname[IFNAMSIZ] __attribute__((aligned(sizeof(long))));
 	const struct xt_physdev_info *info = par->matchinfo;