net/mlx5e: Remove accesses to priv for low level IPsec FS code

mlx5 priv structure is driver main structure that holds high level data.
That information is not needed for IPsec flow steering logic and the
pointer to mlx5e_priv was not supposed to be passed in the first place.

This change "cleans" the logic to rely on internal to IPsec structures
without touching global mlx5e_priv.

Reviewed-by: Raed Salem <raeds@nvidia.com>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>