ACPI/NUMA: Squash acpi_numa_slit_init() into acpi_parse_slit()

After removing architectural code the helper function
acpi_numa_slit_init() is no longer needed. Squash it into
acpi_parse_slit(). No functional changes intended.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Robert Richter <rrichter@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>