platform/chrome: cros_ec: Report EC panic as uevent

Create a uevent when an EC panic is detected. This will allow udev rules
to trigger when a panic occurs. For example, a udev rule could be added to
capture an EC coredump. This approach avoids the need to stuff all the
processing into the driver.

Signed-off-by: Rob Barnes <robbarnes@google.com>
Reviewed-by: Prashant Malani <pmalani@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20230509232624.3120347-1-robbarnes@google.com