selftests/resctrl: Disable MBA and MBM tests for AMD

For now, disable MBA and MBM tests for AMD. Deciding test pass/fail
is not clear right now. We can enable when we have some clarity.

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>