powerpc: Move most remaining ppc64 files over to arch/powerpc

Also deletes files in arch/ppc64 that are no longer used now that
we don't compile with ARCH=ppc64 any more.

Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c523029..c5c3f42 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -932,6 +932,7 @@
 
 config KPROBES
 	bool "Kprobes (EXPERIMENTAL)"
+	depends on PPC64
 	help
 	  Kprobes allows you to trap at almost any kernel address and
 	  execute a callback function.  register_kprobe() establishes