[NETFILTER]: annotate rest of nf_conntrack_* with const

Signed-off-by: Jan Engelhardt <jengelh@computergmbh.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/netfilter/nf_conntrack_ftp.c b/net/netfilter/nf_conntrack_ftp.c
index 7eff876bb..87ca39b 100644
--- a/net/netfilter/nf_conntrack_ftp.c
+++ b/net/netfilter/nf_conntrack_ftp.c
@@ -350,8 +350,9 @@
 		enum ip_conntrack_info ctinfo)
 {
 	unsigned int dataoff, datalen;
-	struct tcphdr _tcph, *th;
-	char *fb_ptr;
+	const struct tcphdr *th;
+	struct tcphdr _tcph;
+	const char *fb_ptr;
 	int ret;
 	u32 seq;
 	int dir = CTINFO2DIR(ctinfo);