powerpc: Fix failure to shutdown with CPU hotplug

I tracked down the shutdown regression to CPUs not dying
when being shut down during power-off. This turns out to
be due to the system_state being SYSTEM_POWER_OFF, which
this code doesn't take as a valid state for shutting off
CPUs in.

This has never made sense to me, but when I added hotplug
code to implement hibernate I only "made it work" and did
not question the need to check the system_state. Thomas
Gleixner helped me dig, but the only thing we found is
that it was added with the original commit that added CPU
hotplug support.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Joel Schopp <jschopp@austin.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/idle.c

@@ -34,11 +34,7 @@
 #include <asm/smp.h>
 
 #ifdef CONFIG_HOTPLUG_CPU
-/* this is used for software suspend, and that shuts down
- * CPUs even while the system is still booting... */
-#define cpu_should_die()	(cpu_is_offline(smp_processor_id()) && \
-				   (system_state == SYSTEM_RUNNING     \
-				 || system_state == SYSTEM_BOOTING))
+#define cpu_should_die()	cpu_is_offline(smp_processor_id())
 #else
 #define cpu_should_die()	0
 #endif