Bluetooth: Fix VIRTIO_ID_BT assigned number

It turned out that the VIRTIO_ID_* are not assigned in the virtio_ids.h
file in the upstream kernel. Picking the next free one was wrong and
there is a process that has been followed now.

See https://github.com/oasis-tcs/virtio-spec/issues/108

 for details.

Fixes: afd2daa2 ("Bluetooth: Add support for virtio transport driver")
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>