x86/intel_rdt/cqm: Add mkdir support for RDT monitoring
Resource control groups can be created using mkdir in resctrl fs(rdtgroup). In order to extend the resctrl interface to support monitoring the control groups, extend the current mkdir to support resource monitoring also. This allows the rdtgroup created under the root directory to be able to both control and monitor resources (ctrl_mon group). The ctrl_mon groups are associated with one CLOSID like the legacy rdtgroups and one RMID(Resource monitoring ID) as well. Hardware uses RMID to track the resource usage. Once either of the CLOSID or RMID are exhausted, the mkdir fails with -ENOSPC. If there are RMIDs in limbo list but not free an -EBUSY is returned. User can also monitor a subset of the ctrl_mon rdtgroup's tasks/cpus using the monitor groups. The monitor groups are created using mkdir under the "mon_groups" directory in every ctrl_mon group. [Merged Tony's code: Removed a lot of common mkdir code, a fix to handling of the list of the child rdtgroups and some cleanups in list traversal. Also the changes to have similar alloc and free for CLOS/RMID and return -EBUSY when RMIDs are in limbo and not free] Signed-off-by:Tony Luck <tony.luck@intel.com> Signed-off-by: