Per the UEFIv2.7 spec, EFI_DEVICE_ERROR is returned when the serial device is not functioning correctly. Update the description to avoid confusion. Contributed-under: Tianocore Contribution Agreement 1.1 Signed-off-by: Julien Grall <julien.grall@linaro.org> Reviewed-by: Star Zeng <star.zeng@intel.com> Reviewed-by: Laszlo Ersek <lersek@redhat.com>