Revert "decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb"

This reverts commit 85eac2ba.

There is an updated version of this fix which we should
use instead.
Signed-off-by: David S. Miller <davem@davemloft.net>

net/decnet/netfilter/dn_rtmsg.c

@@ -102,9 +102,7 @@ static inline void dnrmg_receive_user_skb(struct sk_buff *skb)
 {
 	struct nlmsghdr *nlh = nlmsg_hdr(skb);
 
-	if (skb->len < sizeof(nlh->nlmsg_len) ||
-	    nlh->nlmsg_len < sizeof(*nlh) ||
-	    skb->len < nlh->nlmsg_len)
+	if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
 		return;
 
 	if (!netlink_capable(skb, CAP_NET_ADMIN))