trivial: uefi: clarify errors related to secure boot
trivial: uefi: clarify errors related to secure boot

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