nft: family_ops: Pass nft_handle to 'rule_to_cs' callback

nft: family_ops: Pass nft_handle to 'rule_to_cs' callback

This is the actual callback used to parse nftables rules. Pass
nft_handle to it so it can access the cache (and possible sets therein).

Having to pass nft_handle to nft_rule_print_save() allows to simplify it
a bit since no family ops lookup has to be done anymore.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>