Log overflow is marked by a separate trace message.

Simulate a log with lots of messages and flag overflow until space is
cleared.
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20221216-cxl-ev-log-v7-8-2316a5c8f7d8@intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>