vfio/mlx5: Run the SAVE state command in an async mode

Use the PF asynchronous command mode for the SAVE state command.

This enables returning earlier to user space upon issuing successfully
the command and improve latency by let things run in parallel.

Link: https://lore.kernel.org/r/20220510090206.90374-5-yishaih@nvidia.com


Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>