powerpc/smp: Don't expose per-cpu "cpu_state" array

Instead, keep it static, expose an accessor and use that from
the PowerMac code. Avoids easy namespace collisions and will
make it easier to consolidate with other implementations.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 7e99771..a902a0d 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -45,7 +45,7 @@
 int generic_cpu_disable(void);
 void generic_cpu_die(unsigned int cpu);
 void generic_mach_cpu_die(void);
-DECLARE_PER_CPU(int, cpu_state);
+void generic_set_cpu_dead(unsigned int cpu);
 #endif
 
 #ifdef CONFIG_PPC64