powerpc: Merge in 64-bit powermac support.

This brings in a lot of changes from arch/ppc64/kernel/pmac_*.c to
arch/powerpc/platforms/powermac/*.c and makes various minor tweaks
elsewhere.  On the powermac we now initialize ppc_md by copying
the whole pmac_md structure into it, which required some changes in
the ordering of initializations of individual fields of it.

Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/include/asm-ppc64/system.h b/include/asm-ppc64/system.h
index d1e0093..2e17ef7 100644
--- a/include/asm-ppc64/system.h
+++ b/include/asm-ppc64/system.h
@@ -148,6 +148,8 @@
 extern struct task_struct * _switch(struct thread_struct *prev,
 				    struct thread_struct *next);
 
+extern int powersave_nap;	/* set if nap mode can be used in idle loop */
+
 /*
  * Atomic exchange
  *