nfp: flower-ct: fill ct metadata check function

Fill in check_meta stub to check that ct_metadata action fields in
the nft flow matches the ct_match data of the post_ct flow.

Signed-off-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: Yinjun Zhang <yinjun.zhang@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>