virtio_vdpa: reject invalid vq indices

Do not call vDPA drivers' callbacks with vq indicies larger than what
the drivers indicate that they support.  vDPA drivers do not bounds
check the indices.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Link: https://lore.kernel.org/r/20210701114652.21956-1-vincent.whitchurch@axis.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>