vdpa/mlx5: fix virtio queue unset

vdpa/mlx5: fix virtio queue unset

When a virtq is destroyed, the SW should be able to continue the virtq
processing from where the HW stopped.

The current destroy behavior in the driver saves the virtq state (used
and available indexes) only when LM is requested.
So, when LM is not requested the queue state is not saved and the SW
indexes stay invalid.

Save the virtq state in the virtq destroy process.

Fixes: bff735011078 ("vdpa/mlx5: prepare virtio queues")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Xueming Li <xuemingl@mellanox.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>