vdpa/mlx5: Use async API for vq modify commands

vdpa/mlx5: Use async API for vq modify commands

Switch firmware vq modify command to be issued via the async API to
allow future parallelization. The new refactored function applies the
modify on a range of vqs and waits for their execution to complete.

For now the command is still used in a serial fashion. A later patch
will switch to modifying multiple vqs in parallel.

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Message-Id: <20240816090159.1967650-6-dtatulea@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>