[NETFILTER]: add some consts, remove some casts

Make a number of variables const and/or remove unneeded casts.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netfilter/xt_connbytes.c b/net/netfilter/xt_connbytes.c
index 1254178..99c246e 100644
--- a/net/netfilter/xt_connbytes.c
+++ b/net/netfilter/xt_connbytes.c
@@ -26,7 +26,7 @@
       bool *hotdrop)
 {
 	const struct xt_connbytes_info *sinfo = matchinfo;
-	struct nf_conn *ct;
+	const struct nf_conn *ct;
 	enum ip_conntrack_info ctinfo;
 	u_int64_t what = 0;	/* initialize to make gcc happy */
 	u_int64_t bytes = 0;