xfrm_user: constify netlink dispatch table

There is no need to modify the netlink dispatch table at runtime.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_user.c

@@ -2315,7 +2315,7 @@ static const struct nla_policy xfrma_policy[XFRMA_MAX+1] = {
 	[XFRMA_SA_EXTRA_FLAGS]	= { .type = NLA_U32 },
 };
 
-static struct xfrm_link {
+static const struct xfrm_link {
 	int (*doit)(struct sk_buff *, struct nlmsghdr *, struct nlattr **);
 	int (*dump)(struct sk_buff *, struct netlink_callback *);
 	int (*done)(struct netlink_callback *);
@@ -2349,7 +2349,7 @@ static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
 	struct net *net = sock_net(skb->sk);
 	struct nlattr *attrs[XFRMA_MAX+1];
-	struct xfrm_link *link;
+	const struct xfrm_link *link;
 	int type, err;
 
 	type = nlh->nlmsg_type;