net/mlx5: Remove ipsec_ops function table

There is only one IPsec implementation and ipsec_ops is not needed
at all in this situation. Together with removal of ipsec_ops, we can
drop the entry checks as these functions are called for IPsec devices
only.

Link: https://lore.kernel.org/r/bc8dd1c8a77b65dbf5e2cf92c813ffaca2505c5f.1649232994.git.leonro@nvidia.com
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>