selftests/resctrl: Add basic resctrl file system operations and data

The basic resctrl file system operations and data are added for future
usage by resctrl selftest tool.

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Co-developed-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
Co-developed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>