net/mlx5e: kTLS, Remove unnecessary per-callback completion

Waiting on a completion object for each callback before cleaning up their
async contexts is not necessary, as this is already implied in the
mlx5_cmd_cleanup_async_ctx() API.

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Gal Pressman <gal@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>