x86: make memory_add_physaddr_to_nid depend on MEMORY_HOTPLUG

memory_add_physaddr_to_nid() is only used in the
CONFIG_MEMORY_HOTPLUG_SPARSE || CONFIG_ACPI_HOTPLUG_MEMORY case.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/mm/srat_64.c

@@ -522,6 +522,7 @@ int __node_distance(int a, int b)
 
 EXPORT_SYMBOL(__node_distance);
 
+#if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) || defined(CONFIG_ACPI_HOTPLUG_MEMORY)
 int memory_add_physaddr_to_nid(u64 start)
 {
 	int i, ret = 0;
@@ -533,4 +534,4 @@ int memory_add_physaddr_to_nid(u64 start)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
-
+#endif