The clock/timer APIs are not application facing APIs, however, similar
to arch_ and a few other APIs they are available to implement drivers
and add support for new hardware and are documented and available to be
used outside of the clock/kernel subsystems.
Remove the leading z_ and provide them as clock_* APIs for someone
writing a new timer driver to use.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Add some error condition or testing cases to verify whether the
robustness of API. Such as give a NULL to some API and check
the response if get result that we were expacted.
Signed-off-by: Jian Kang <jianx.kang@intel.com>
