qdev: add bit property type This adds "bit" property type, which is a boolean stored in a 32 bit integer field, with legal values on and off. Will be used by virtio for feature bits. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>