ras-events: make returned error code consistent

ras-events: make returned error code consistent

- Rework the returned code logic to be more consistent;
  - error codes will be using negative values;
  - positive values indicate special return codes.
- Don't bloat the logs with lots of error messages due to
  unsupported traces;
- Ensure that the number of CPUs will probably retrieved or bail out;
- Don't bail if it can't setup a monotone clock: it is better
  to have a wrong timestamp than no log at all.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>