selftests/resctrl: Print a message if the result of MBM&CMT tests is failed on Intel CPU

According to "Intel Resource Director Technology (Intel RDT) on
2nd Generation Intel Xeon Scalable Processors Reference Manual",
When the Intel Sub-NUMA Clustering(SNC) feature is enabled,
Intel CMT and MBM counters may not be accurate.

However, there does not seem to be an architectural way to detect
if SNC is enabled.

If the result of MBM&CMT test fails on Intel CPU,
print a message to let users know a possible cause of failure.

Acked-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>