selftests/resctrl: Add ->init() callback into resctrl_val_param

selftests/resctrl: Add ->init() callback into resctrl_val_param

The struct resctrl_val_param is there to customize behavior inside
resctrl_val() which is currently not used to full extent and there are
number of strcmp()s for test name in resctrl_val done by resctrl_val().

Create ->init() hook into the struct resctrl_val_param to cleanly
do per test initialization.

Remove also unused branches to setup paths and the related #defines
for CMT test.

While touching kerneldoc, make the adjacent line consistent with the
newly added form (callback vs call back).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>