powerpc: Add NAP mode support on Power7 in HV mode

Wakeup comes from the system reset handler with a potential loss of
the non-hypervisor CPU state. We save the non-volatile state on the
stack and a pointer to it in the PACA, which the system reset handler
uses to restore things

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
index e4f0191..493dbb3 100644
--- a/arch/powerpc/include/asm/machdep.h
+++ b/arch/powerpc/include/asm/machdep.h
@@ -267,6 +267,7 @@
 
 extern void e500_idle(void);
 extern void power4_idle(void);
+extern void power7_idle(void);
 extern void ppc6xx_idle(void);
 extern void book3e_idle(void);