ACPI: add NFIT and HMAT to the initrd override list

These tables, NFIT and HMAT, are essential for describing
next-generation platform memory topologies and performance
characteristics. Allow them to be overridden for debug and test and
purposes.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>