netfilter: nf_tables: A better name for nft_obj_filter

[ Upstream commit ecf49cad ]

Name it for what it is supposed to become, a real nft_obj_dump_ctx. No
functional change intended.

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>