netfilter: nft_ct: include direction when dumping NFT_CT_L3PROTOCOL key

one nft userspace test case fails with

'ct l3proto original ipv4' mismatches 'ct l3proto ipv4'

... because NFTA_CT_DIRECTION attr is missing.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>