powerpc/pseries: Fix CONFIG_NUMA=n build

The build is failing with CONFIG_NUMA=n and some compiler versions:

  arch/powerpc/platforms/pseries/hotplug-cpu.o: In function `dlpar_online_cpu':
  hotplug-cpu.c:(.text+0x12c): undefined reference to `timed_topology_update'
  arch/powerpc/platforms/pseries/hotplug-cpu.o: In function `dlpar_cpu_remove':
  hotplug-cpu.c:(.text+0x400): undefined reference to `timed_topology_update'

Fix it by moving the empty version of timed_topology_update() into the
existing #ifdef block, which has the right guard of SPLPAR && NUMA.

Fixes: cee5405 ("powerpc/hotplug: Improve responsiveness of hotplug change")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/topology.h

@@ -91,6 +91,7 @@ extern int start_topology_update(void);
 extern int stop_topology_update(void);
 extern int prrn_is_enabled(void);
 extern int find_and_online_cpu_nid(int cpu);
+extern int timed_topology_update(int nsecs);
 #else
 static inline int start_topology_update(void)
 {
@@ -108,16 +109,12 @@ static inline int find_and_online_cpu_nid(int cpu)
 {
 	return 0;
 }
+static inline int timed_topology_update(int nsecs)
+{
+	return 0;
+}
 #endif /* CONFIG_NUMA && CONFIG_PPC_SPLPAR */
 
-#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_NEED_MULTIPLE_NODES)
-#if defined(CONFIG_PPC_SPLPAR)
-extern int timed_topology_update(int nsecs);
-#else
-#define	timed_topology_update(nsecs)
-#endif /* CONFIG_PPC_SPLPAR */
-#endif /* CONFIG_HOTPLUG_CPU || CONFIG_NEED_MULTIPLE_NODES */
-
 #include <asm-generic/topology.h>
 
 #ifdef CONFIG_SMP