ACPI: MRRM: Minimal parse of ACPI MRRM table

The resctrl file system code needs to know how many region tags
are supported. Parse the ACPI MRRM table and save the max_mem_region
value.

Provide a function for resctrl to collect that value.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://patch.msgid.link/20250505173819.419271-2-tony.luck@intel.com


Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>