net: constify struct inet6_protocol

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 2d9cbaa..237e2db 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -159,7 +159,7 @@
 
 static int ip6_input_finish(struct sk_buff *skb)
 {
-	struct inet6_protocol *ipprot;
+	const struct inet6_protocol *ipprot;
 	unsigned int nhoff;
 	int nexthdr, raw;
 	u8 hash;