vhost-vdpa: Handle the failure of vdpa_reset()

The vdpa_reset() may fail now. This adds check to its return
value and fail the vhost_vdpa_open().

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20210831103634.33-7-xieyongji@bytedance.com


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