generic_linux: Remove forbidden chars from device_model
generic_linux: Remove forbidden chars from device_model

Fix for Chromebook Plus and possibly other devices - removes forbidden
characters from the device_model such as the null character which was
causing a problem with getters getting file names including device_model.

bjackman/workload-automation,jimboatarm/workload-automation,jimboatarm/workload-automation,jimboatarm/workload-automation,jimboatarm/workload-automation,bjackman/workload-automation,bjackman/workload-automation,bjackman/workload-automation,bjackman/workload-automation,jimboatarm/workload-automation,bjackman/workload-automation,jimboatarm/workload-automation