net/mlx5: Refactor tc flow attributes structure

In order to support chains and connection tracking offload for
nic flows, there's a need to introduce a common flow attributes
struct so that these features can be agnostic and have access to
a single attributes struct, regardless of the flow type.

Therefore, a new tc flow attributes format is introduced to allow
access to attributes that are common to eswitch and nic flows.

The common attributes will always get allocated for the new flows,
regardless of their type, while the type specific attributes are
separated into different structs and will be allocated based on the
flow type to avoid memory waste.

When allocating the flow attributes the caller provides the flow
steering namespace and according the namespace type the additional
space for the extra, type specific, attributes is determined and
added to the total attribute allocation size.

In addition, the attributes that are going to be common to both
flow types are moved to the common attributes struct.

Signed-off-by: Ariel Levkovich <lariel@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>