greybus: bundle: create GB_DEVICE_ID_BAD

Use a "name" for when we don't have a valid device id yet, instead of a
magic value of 0xff.

Reported-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
Reviewed-by: Alex Elder <elder@linaro.org>