ACPI / NUMA: Move acpi_numa_arch_fixup() to ia64 only

Since acpi_numa_arch_fixup() is only used in arch ia64, move it there
to make a generic interface easier. This avoids empty function stubs
or some complex kconfig options for x86 and arm64.

Signed-off-by: Robert Richter <rrichter@cavium.com>
Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>