trivial: Fix compile warning with newer libgusb versions
trivial: Fix compile warning with newer libgusb versions

hughsie/fwupd,fwupd/fwupd,fwupd/fwupd,fwupd/fwupd,hughsie/fwupd,hughsie/fwupd,hughsie/fwupd,fwupd/fwupd