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/udbg.h b/include/asm-ppc64/udbg.h
index c786604..8192fb8 100644
--- a/include/asm-ppc64/udbg.h
+++ b/include/asm-ppc64/udbg.h
@@ -28,4 +28,7 @@
 extern void __init ppcdbg_initialize(void);
 
 extern void udbg_init_uart(void __iomem *comport, unsigned int speed);
+
+struct device_node;
+extern void udbg_init_scc(struct device_node *np);
 #endif