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.
diff --git a/arch/x86/mm/discontig_32.c b/arch/x86/mm/discontig_32.c
index 0d28b4b..8b4eac0 100644
--- a/arch/x86/mm/discontig_32.c
+++ b/arch/x86/mm/discontig_32.c
@@ -467,4 +467,8 @@
 acpi_numa_processor_affinity_init(struct acpi_srat_cpu_affinity *pa)
 {
 }
+
+void __init acpi_numa_arch_fixup(void)
+{
+}
 #endif