Refine handling of zero-valued max_event_level_reports

[apasel422]

Should it be an error to set max_event_level_reports to 0 but also set the event_report_window or event_report_windows fields? Currently the spec permits this, and properly restricts the number of reports, though arguably it is more inline with the rest of the spec to make it a source-registration error to help detect things like typos.