nfp: flower: refactor function "is_post_ct_flow"

'ct_clear' action only or no ct action is supported for 'post_ct_flow'.
But in scenario of multiple ct zones, one non 'ct_clear' ct action or
more ct actions, including 'ct_clear action', may be present in one flow
rule. If ct state match key is 'ct_established', the flow rule is still
expected to be classified as 'post_ct_flow'. Check ct status first in
function "is_post_ct_flow" to achieve this.

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>