net/mlx5e: Open mlx5 driver to accept IPsec packet offload

Enable configuration of IPsec packet offload through XFRM state add
interface together with moving specific to IPsec packet mode limitations
to specific switch-case section.

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