netfilter: nft_lookup: remove superfluous element found check

We already checked for !found just a bit before:

        if (!found) {
                regs->verdict.code = NFT_BREAK;
                return;
        }

        if (found && set->flags & NFT_SET_MAP)
            ^^^^^

So this redundant check can just go away.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>