vdpa/mlx5: Support different address spaces for control and data

Partition virtqueues to two different address spaces: one for control
virtqueue which is implemented in software, and one for data virtqueues.

Based-on: <20220526124338.36247-1-eperezma@redhat.com>
Signed-off-by: Eli Cohen <elic@nvidia.com>
Message-Id: <20220714113927.85729-3-elic@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>