Bluetooth: Fix Class of Device indication when powering off

When a HCI device is powered off the Management interface specification
dictates that the class of device value is indicated as zero. This patch
fixes sending of the appropriate class of device changed event when a
HCI device is powered off.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>