vdpa/vp_vdpa : add vdpa tool support in vp_vdpa

this patch is to add the support for vdpa tool in vp_vdpa
here is the example steps

modprobe vp_vdpa
modprobe vhost_vdpa
echo 0000:00:06.0>/sys/bus/pci/drivers/virtio-pci/unbind
echo 1af4 1041 > /sys/bus/pci/drivers/vp-vdpa/new_id

vdpa dev add name vdpa1 mgmtdev pci/0000:00:06.0

Signed-off-by: Cindy Lu <lulu@redhat.com>
Message-Id: <20220429091030.547434-1-lulu@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>