net/mlx5: IPsec, Refactor SA handle creation and destruction

Currently the SA handle is created and managed as part of the common
code for different IPsec supporting HW, this handle is passed to HW
to be used on Rx to identify the SA handle that was used to
return the xfrm state to stack.

The above implementation pose a limitation on managing this handle.

Refactor by moving management of this field to the specific HW code.

Downstream patches will introduce the Connect-X support for IPsec that
will use this handle differently than current implementation.

Signed-off-by: Raed Salem <raeds@mellanox.com>
Reviewed-by: Boris Pismenny <borisp@mellanox.com>
Reviewed-by: Huy Nguyen <huyn@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>