ipv6: constify the skb pointer of ipv6_find_tlv().

Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 4e279a8..24a5ebe 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -945,7 +945,7 @@
 int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset, int target,
 		  unsigned short *fragoff, int *fragflg);
 
-int ipv6_find_tlv(struct sk_buff *skb, int offset, int type);
+int ipv6_find_tlv(const struct sk_buff *skb, int offset, int type);
 
 struct in6_addr *fl6_update_dst(struct flowi6 *fl6,
 				const struct ipv6_txoptions *opt,