netfilter: nft_osf: restrict osf to ipv4, ipv6 and inet families

[ Upstream commit 5f3b7aae ]

As it was originally intended, restrict extension to supported families.

Fixes: b96af92d

 ("netfilter: nf_tables: implement Passive OS fingerprint module in nft_osf")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>