powerpc: Merge enough to start building in arch/powerpc.

This creates the directory structure under arch/powerpc and a bunch
of Kconfig files.  It does a first-cut merge of arch/powerpc/mm,
arch/powerpc/lib and arch/powerpc/platforms/powermac.  This is enough
to build a 32-bit powermac kernel with ARCH=powerpc.

For now we are getting some unmerged files from arch/ppc/kernel and
arch/ppc/syslib, or arch/ppc64/kernel.  This makes some minor changes
to files in those directories and files outside arch/powerpc.

The boot directory is still not merged.  That's going to be interesting.

Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/prep/Kconfig

@@ -0,0 +1,22 @@
+
+config PREP_RESIDUAL
+	bool "Support for PReP Residual Data"
+	depends on PPC_PREP
+	help
+	  Some PReP systems have residual data passed to the kernel by the
+	  firmware.  This allows detection of memory size, devices present and
+	  other useful pieces of information.  Sometimes this information is
+	  not present or incorrect, in which case it could lead to the machine 
+	  behaving incorrectly.  If this happens, either disable PREP_RESIDUAL
+	  or pass the 'noresidual' option to the kernel.
+
+	  If you are running a PReP system, say Y here, otherwise say N.
+
+config PROC_PREPRESIDUAL
+	bool "Support for reading of PReP Residual Data in /proc"
+	depends on PREP_RESIDUAL && PROC_FS
+	help
+	  Enabling this option will create a /proc/residual file which allows
+	  you to get at the residual data on PReP systems.  You will need a tool
+	  (lsresidual) to parse it.  If you aren't on a PReP system, you don't
+	  want this.