selftests/resctrl: Remove mongrp from CMT test

selftests/resctrl: Remove mongrp from CMT test

The CMT selftest instantiates a monitor group to read LLC occupancy.
Since the test also creates a control group, it is unnecessary to
create another one for monitoring because control groups already
provide monitoring too.

Remove the unnecessary monitor group from the CMT selftest.

Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
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>