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>

drivers/macintosh/via-pmu.c

@@ -405,7 +405,7 @@ static int __init via_pmu_start(void)
 	bright_req_2.complete = 1;
 	batt_req.complete = 1;
 
-#ifdef CONFIG_PPC32
+#if defined(CONFIG_PPC32) && !defined(CONFIG_PPC_MERGE)
 	if (pmu_kind == PMU_KEYLARGO_BASED)
 		openpic_set_irq_priority(vias->intrs[0].line,
 					 OPENPIC_PRIORITY_DEFAULT + 1);