Kconfig: consolidate the "Kernel hacking" menu

Move the source of lib/Kconfig.debug and arch/$(ARCH)/Kconfig.debug to
the top-level Kconfig.  For two architectures that means moving their
arch-specific symbols in that menu into a new arch Kconfig.debug file,
and for a few more creating a dummy file so that we can include it
unconditionally.

Also move the actual 'Kernel hacking' menu to lib/Kconfig.debug, where
it belongs.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 8838d11..26d3ff7 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1,3 +1,5 @@
+menu "Kernel hacking"
+
 menu "printk and dmesg options"
 
 config PRINTK_TIME
@@ -2034,3 +2036,7 @@
 	  if the driver using a given range cannot be disabled.
 
 	  If in doubt, say Y.
+
+source "arch/$(SRCARCH)/Kconfig.debug"
+
+endmenu # Kernel hacking