x86, numaq 32-bit: build fix

fix:

drivers/built-in.o: In function `acpi_numa_init':
: undefined reference to `acpi_numa_arch_fixup'

which can happen with ACPI && NUMAQ.

arch/x86/mm/discontig_32.c

@@ -467,4 +467,8 @@ void __init
 acpi_numa_processor_affinity_init(struct acpi_srat_cpu_affinity *pa)
 {
 }
+
+void __init acpi_numa_arch_fixup(void)
+{
+}
 #endif