dcbnl: Use type safe nlmsg_data()

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dcb/dcbnl.c

@@ -1659,7 +1659,7 @@ static int dcb_doit(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 {
 	struct net *net = sock_net(skb->sk);
 	struct net_device *netdev;
-	struct dcbmsg  *dcb = (struct dcbmsg *)NLMSG_DATA(nlh);
+	struct dcbmsg *dcb = nlmsg_data(nlh);
 	struct nlattr *tb[DCB_ATTR_MAX + 1];
 	u32 pid = skb ? NETLINK_CB(skb).pid : 0;
 	int ret = -EINVAL;