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>
diff --git a/arch/ppc/kernel/setup.c b/arch/ppc/kernel/setup.c
index 77fecfba..1b891b8 100644
--- a/arch/ppc/kernel/setup.c
+++ b/arch/ppc/kernel/setup.c
@@ -83,6 +83,8 @@
 		unsigned long r5, unsigned long r6, unsigned long r7);
 extern void chrp_init(unsigned long r3, unsigned long r4,
 		unsigned long r5, unsigned long r6, unsigned long r7);
+
+dev_t boot_dev;
 #endif /* CONFIG_PPC_MULTIPLATFORM */
 
 #ifdef CONFIG_MAGIC_SYSRQ
@@ -405,11 +407,13 @@
 			_machine = _MACH_prep;
 	}
 
+#ifdef CONFIG_PPC_PREP
 	/* not much more to do here, if prep */
 	if (_machine == _MACH_prep) {
 		prep_init(r3, r4, r5, r6, r7);
 		return;
 	}
+#endif
 
 	/* prom_init has already been called from __start */
 	if (boot_infos)
@@ -480,12 +484,16 @@
 #endif /* CONFIG_ADB */
 
 	switch (_machine) {
+#ifdef CONFIG_PPC_PMAC
 	case _MACH_Pmac:
 		pmac_init(r3, r4, r5, r6, r7);
 		break;
+#endif
+#ifdef CONFIG_PPC_CHRP
 	case _MACH_chrp:
 		chrp_init(r3, r4, r5, r6, r7);
 		break;
+#endif
 	}
 }