netfilter: nf_tables: restrict tunnel object to NFPROTO_NETDEV

[ Upstream commit 776d4516 ]

Bail out on using the tunnel dst template from other than netdev family.
Add the infrastructure to check for the family in objects.

Fixes: af308b94

 ("netfilter: nf_tables: add tunnel support")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>