virtio_vdpa: don't warn when fail to disable vq

There's no guarantee that the device can disable a specific virtqueue
through set_vq_ready(). One example is the modern virtio-pci
device. So this patch removes the warning.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210104065503.199631-19-jasowang@redhat.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>