Bluetooth: hci_core: Disable works on hci_unregister_dev

This make use of disable_work_* on hci_unregister_dev since the hci_dev is
about to be freed new submissions are not disarable.

Fixes: 0d151a10 ("Bluetooth: hci_core: cancel all works upon hci_unregister_dev()")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>