xtables: pass format to nft_rule_save()

Preparing ebtables-save implementation, allow for callers to pass format
bits to nft_rule_save() instead of just the 'counters' boolean.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>
3 files changed