powerpc: Unify the 32 and 64 bit idle loops

This unifies the 32-bit (ARCH=ppc and ARCH=powerpc) and 64-bit idle
loops.  It brings over the concept of having a ppc_md.power_save
function from 32-bit to ARCH=powerpc, which lets us get rid of
native_idle().  With this we will also be able to simplify the idle
handling for pSeries and cell.

Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/platforms/powermac/setup.c b/arch/powerpc/platforms/powermac/setup.c
index 385aab9..c2696d0 100644
--- a/arch/powerpc/platforms/powermac/setup.c
+++ b/arch/powerpc/platforms/powermac/setup.c
@@ -733,7 +733,7 @@
 	.progress		= udbg_progress,
 #ifdef CONFIG_PPC64
 	.pci_probe_mode		= pmac_pci_probe_mode,
-	.idle_loop		= native_idle,
+	.power_save		= power4_idle,
 	.enable_pmcs		= power4_enable_pmcs,
 #ifdef CONFIG_KEXEC
 	.machine_kexec		= default_machine_kexec,