[NETLINK]: Use nlmsg_trim() where appropriate

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 2c7ab10..510ca7f 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -548,7 +548,7 @@
  *
  * Trims the message to the provided mark. Returns -1.
  */
-static inline int nlmsg_trim(struct sk_buff *skb, void *mark)
+static inline int nlmsg_trim(struct sk_buff *skb, const void *mark)
 {
 	if (mark)
 		skb_trim(skb, (unsigned char *) mark - skb->data);