vdpa/mlx5: Introduce async fw command wrapper

vdpa/mlx5: Introduce async fw command wrapper

Introduce a new function mlx5_vdpa_exec_async_cmds() which
wraps the mlx5_core async firmware command API in a way
that will be used to parallelize certain operation in this
driver.

The wrapper deals with the case when mlx5_cmd_exec_cb() returns
EBUSY due to the command being throttled.

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Message-Id: <20240816090159.1967650-4-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>