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/ipcomp6.c b/net/ipv6/ipcomp6.c
index 79c172f..2f2a5ca 100644
--- a/net/ipv6/ipcomp6.c
+++ b/net/ipv6/ipcomp6.c
@@ -178,7 +178,7 @@
 	.hdr_offset	= xfrm6_find_1stfragopt,
 };
 
-static struct inet6_protocol ipcomp6_protocol =
+static const struct inet6_protocol ipcomp6_protocol =
 {
 	.handler	= xfrm6_rcv,
 	.err_handler	= ipcomp6_err,