platform/chrome: sensorhub: Add trace events for sample

platform/chrome: sensorhub: Add trace events for sample

[ Upstream commit d453ceb6549af8798913de6a20444cb7200fdb69 ]

Add trace event to report samples and their timestamp coming from the
EC. It allows to check if the timestamps are correct and the filter is
working correctly without introducing too much latency.

To enable these events:

cd /sys/kernel/debug/tracing/
echo 1 > events/cros_ec/enable
echo 0 > events/cros_ec/cros_ec_request_start/enable
echo 0 > events/cros_ec/cros_ec_request_done/enable
echo 1 > tracing_on
cat trace_pipe
Observe event flowing:
irq/105-chromeo-95      [000] ....   613.659758: cros_ec_sensorhub_timestamp: ...
irq/105-chromeo-95      [000] ....   613.665219: cros_ec_sensorhub_filter: dx: ...

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>