powerpc: Move definitions of secondary CPU spinloop to header file

Those definitions are currently declared extern in the .c file where
they are used, move them to a header file instead.

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 c25f73d..e782f43 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -148,6 +148,15 @@
 extern void arch_send_call_function_single_ipi(int cpu);
 extern void arch_send_call_function_ipi(cpumask_t mask);
 
+/* Definitions relative to the secondary CPU spin loop
+ * and entry point. Not all of them exist on both 32 and
+ * 64-bit but defining them all here doesn't harm
+ */
+extern void generic_secondary_smp_init(void);
+extern unsigned long __secondary_hold_spinloop;
+extern unsigned long __secondary_hold_acknowledge;
+extern char __secondary_hold;
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __KERNEL__ */