[XFRM]: constify 'struct xfrm_type'

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c
index fb0d07a..379c8e0 100644
--- a/net/ipv6/ah6.c
+++ b/net/ipv6/ah6.c
@@ -515,7 +515,7 @@
 	kfree(ahp);
 }
 
-static struct xfrm_type ah6_type =
+static const struct xfrm_type ah6_type =
 {
 	.description	= "AH6",
 	.owner		= THIS_MODULE,