net/mlx5e: Refactor ct to use post action infrastructure

Move post action table management to common library providing
add/del/get API. Refactor the ct action offload to use the common
API.

Signed-off-by: Chris Mi <cmi@nvidia.com>
Reviewed-by: Oz Shlomo <ozsh@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>