nfp: flower: refactor function "is_pre_ct_flow"

In the scenario of multiple ct zones, ct state key match and ct action
is present in one flow rule, the flow rule is classified to post_ct_flow
in design.

There is no ct state key match for pre ct flow, the judging condition
is added to function "is_pre_ct_flow".

Chain_index is another field for judging which flows are pre ct flow
If chain_index not 0, the flow is not pre ct flow.

Signed-off-by: Wentao Jia <wentao.jia@corigine.com>
Acked-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>