nfp: flower-ct: add ct zone table

Add initial zone table to nfp_flower_priv. This table will be used
to store all the information required to offload conntrack.

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>