netfilter: nfnetlink: add missing __be16 cast

Sparse flags this as suspicious, because this compares
integer with a be16 with no conversion.

Its a compat check for old userspace that sends host byte order,
so force a be16 cast here.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nfnetlink.c

@@ -626,7 +626,7 @@ static void nfnetlink_rcv_skb_batch(struct sk_buff *skb, struct nlmsghdr *nlh)
 	nfgenmsg = nlmsg_data(nlh);
 	skb_pull(skb, msglen);
 	/* Work around old nft using host byte order */
-	if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES)
+	if (nfgenmsg->res_id == (__force __be16)NFNL_SUBSYS_NFTABLES)
 		res_id = NFNL_SUBSYS_NFTABLES;
 	else
 		res_id = ntohs(nfgenmsg->res_id);