trivial: fu-tool: correct argument type for `--prepare` and `--cleanup`
trivial: fu-tool: correct argument type for `--prepare` and `--cleanup`

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