vdpa/ifcvf: add reviewer

Zhu Lingshan has been writing and reviewing ifcvf patches for
a while now, add as reviewer.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Zhu Lingshan <lingshan.zhu@intel.com>
Acked-by: Jason Wang <jasowang@redhat.com>