usb-storage: Turn drive serial into a qdev property usb-storage.serial It needs to be a qdev property, because it belongs to the drive's guest part. Precedence: commit a0fef654 and 6ced55a5. Bonus: info qtree now shows the serial number. Signed-off-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>