netfilter: nf_tables: Carry reset boolean in nft_obj_dump_ctx

[ Upstream commit a5523390 ]

Relieve the dump callback from having to inspect nlmsg_type upon each
call, just do it once at start of the dump.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Stable-dep-of: bd662c42 ("netfilter: nf_tables: Add locking for NFT_MSG_GETOBJ_RESET requests")
Signed-off-by: Sasha Levin <sashal@kernel.org>