powerpc: clean up after powermac build merge

Complete moving arch/ppc64/kernel/mpic.h,
        include/asm-ppc/reg.h, include/asm-ppc64/kdebug.h
	        and include/asm-ppc64/kprobes.h
Add arch/powerpc/platforms/Makefile and use it from
	arch/powerpc/Makefile
Introduce OLDARCH temporarily so we can point back to
	the originating architecture

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
diff --git a/include/asm-powerpc/kdebug.h b/include/asm-powerpc/kdebug.h
index 7c55abf..9dcbac6 100644
--- a/include/asm-powerpc/kdebug.h
+++ b/include/asm-powerpc/kdebug.h
@@ -1,5 +1,5 @@
-#ifndef _POWERPC_KDEBUG_H
-#define _POWERPC_KDEBUG_H 1
+#ifndef _ASM_POWERPC_KDEBUG_H
+#define _ASM_POWERPC_KDEBUG_H
 
 /* nearly identical to x86_64/i386 code */
 
@@ -39,4 +39,4 @@
 	return notifier_call_chain(&powerpc_die_chain, val, &args);
 }
 
-#endif
+#endif /* _ASM_POWERPC_KDEBUG_H */