net/mlx5e: Allow offloading of ct 'new' match

Allow offloading filters that match on conntrack 'new' state in order to
enable UDP NEW offload in the following patch.

Unhardcode ct 'established' from ct modify header infrastructure code and
determine correct ct state bit according to the metadata action 'cookie'
field.

Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Reviewed-by: Oz Shlomo <ozsh@nvidia.com>
Reviewed-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>