selftests/resctrl: Move cleanups out of individual tests

selftests/resctrl: Move cleanups out of individual tests

Every test calls its cleanup function at the end of it's test function.
After the cleanup function pointer is added to the test framework this
can be simplified to executing the callback function at the end of the
generic test running function.

Make test cleanup functions static and call them from the end of
run_single_test() from the resctrl_test's cleanup function pointer.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>