netfilter: nft_last: copy content when cloning expression

commit 860e8742 upstream.

If the ruleset contains last timestamps, restore them accordingly.
Otherwise, listing after restoration shows never used items.

Fixes: 33a24de3 ("netfilter: nft_last: move stateful fields out of expression data")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>