vdpa: remove msg type of vhost_vdpa

vdpa: remove msg type of vhost_vdpa

It is always VHOST_IOTLB_MSG_V2. We can always make it back per
vhost_dev if needed.

This change makes easier for vhost_vdpa_map and unmap not to depend on
vhost_vdpa but only in VhostVDPAShared.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20231221174322.3130442-10-eperezma@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>