netfilter: nf_tables: prevent shift wrap in nft_chain_parse_hook()

[ Upstream commit 33d1c018179d0a30c39cc5f1682b77867282694b ]

I believe that "hook->num" can be up to UINT_MAX.  Shifting more than
31 bits would is undefined in C but in practice it would lead to shift
wrapping.  That would lead to an array overflow in nf_tables_addchain():

	ops->hook       = hook.type->hooks[ops->hooknum];

Fixes: fe19c04c ("netfilter: nf_tables: remove nhooks field from struct nft_af_info")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>