powerpc: Fix SMP build with disabled CPU hotplugging.

Compiling 2.6.33 with SMP enabled and HOTPLUG_CPU disabled gives me the
following link errors:

  LD      init/built-in.o
  LD      .tmp_vmlinux1
arch/powerpc/platforms/built-in.o: In function `.smp_xics_setup_cpu':
smp.c:(.devinit.text+0x88): undefined reference to `.set_cpu_current_state'
smp.c:(.devinit.text+0x94): undefined reference to `.set_default_offline_state'
arch/powerpc/platforms/built-in.o: In function `.smp_pSeries_kick_cpu':
smp.c:(.devinit.text+0x13c): undefined reference to `.set_preferred_offline_state'
smp.c:(.devinit.text+0x148): undefined reference to `.get_cpu_current_state'
smp.c:(.devinit.text+0x1a8): undefined reference to `.get_cpu_current_state'
make: *** [.tmp_vmlinux1] Error 1

The following change fixes that for me and seems to work as expected.
Signed-off-by: Adam Lackorzynski <adam@os.inf.tu-dresden.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/offline_states.h

@@ -9,10 +9,30 @@ enum cpu_state_vals {
 	CPU_MAX_OFFLINE_STATES
 };
 
+#ifdef CONFIG_HOTPLUG_CPU
 extern enum cpu_state_vals get_cpu_current_state(int cpu);
 extern void set_cpu_current_state(int cpu, enum cpu_state_vals state);
-extern enum cpu_state_vals get_preferred_offline_state(int cpu);
 extern void set_preferred_offline_state(int cpu, enum cpu_state_vals state);
 extern void set_default_offline_state(int cpu);
+#else
+static inline enum cpu_state_vals get_cpu_current_state(int cpu)
+{
+	return CPU_STATE_ONLINE;
+}
+
+static inline void set_cpu_current_state(int cpu, enum cpu_state_vals state)
+{
+}
+
+static inline void set_preferred_offline_state(int cpu, enum cpu_state_vals state)
+{
+}
+
+static inline void set_default_offline_state(int cpu)
+{
+}
+#endif
+
+extern enum cpu_state_vals get_preferred_offline_state(int cpu);
 extern int start_secondary(void);
 #endif