netfilter: nfnetlink_hook: add depends-on nftables

nfnetlink_hook.c: In function 'nfnl_hook_put_nft_chain_info':
nfnetlink_hook.c:76:7: error: implicit declaration of 'nft_is_active'

This macro is only defined when NF_TABLES is enabled.
While its possible to also add an ifdef-guard, the infrastructure
is currently not useful without nf_tables.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 252956528caa ("netfilter: add new hook nfnl subsystem")
Suggested-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>