[POWERPC] Fix build breakage with CONFIG_PPC32

low_cpu_die is called from the CPU hotplug code on 32-bit powermacs,
but it is only defined if CONFIG_PM || CONFIG_CPU_FREQ_PMAC.  This
changes the ifdef so it is defined for CONFIG_HOTPLUG_CPU on 32-bit
machines.
Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/powermac/sleep.S

@@ -45,7 +45,8 @@
 	.section .text
 	.align	5
 
-#if defined(CONFIG_PM) || defined(CONFIG_CPU_FREQ_PMAC)
+#if defined(CONFIG_PM) || defined(CONFIG_CPU_FREQ_PMAC) || \
+    (defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PPC32))
 
 /* This gets called by via-pmu.c late during the sleep process.
  * The PMU was already send the sleep command and will shut us down