vhost-vdpa: introduce uAPI to set group ASID

Follows the vDPA support for associating ASID to a specific virtqueue
group. This patch adds a uAPI to support setting them from userspace.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Gautam Dawar <gdawar@xilinx.com>
Message-Id: <20220330180436.24644-15-gdawar@xilinx.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>