netfilter: nf_tables_offload: fix always true policy is unset check

New smatch warnings:
net/netfilter/nf_tables_offload.c:316 nft_flow_offload_chain() warn: always true condition '(policy != -1) => (0-255 != (-1))'
Reported-by: kbuild test robot <lkp@intel.com>
Fixes: c9626a2c ("netfilter: nf_tables: add hardware offload support")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_offload.c

@@ -313,7 +313,7 @@ static int nft_flow_offload_chain(struct nft_chain *chain,
 	policy = ppolicy ? *ppolicy : basechain->policy;
 
 	/* Only default policy to accept is supported for now. */
-	if (cmd == FLOW_BLOCK_BIND && policy != -1 && policy != NF_ACCEPT)
+	if (cmd == FLOW_BLOCK_BIND && policy == NF_DROP)
 		return -EOPNOTSUPP;
 
 	if (dev->netdev_ops->ndo_setup_tc)