selftests/resctrl: Change name from CBM_MASK_PATH to INFO_PATH

CBM_MASK_PATH is actually the path to resctrl/info.

Change the macro name to correctly indicate what it represents.

[ ij: Tweaked the changelog. ]

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>