netfilter: nft_compat: fix wrong target lookup in nft_target_select_ops()

The code looks for an already loaded target, and the correct list to search
is nft_target_list, not nft_match_list.

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>