ebtables: remove nf_hook_register usage

Similar to ip_register_table, pass nf_hook_ops to ebt_register_table().
This allows to handle hook registration also via pernet_ops and allows
us to avoid use of legacy register_hook api.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>