[POWERPC] New reg.h for the zImage

This patch adds a reg.h to the zImage code, with common definitions
for accessing system registers.  For now, this includes functions for
retrieving the PVR and the stack pointer.  This patch then uses the
new reg.h to let start() display the running stack address without
having to explicitly pass the stack as a parameter from the asm code.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/boot/ops.h b/arch/powerpc/boot/ops.h
index ea5368c..592dc6c 100644
--- a/arch/powerpc/boot/ops.h
+++ b/arch/powerpc/boot/ops.h
@@ -73,7 +73,7 @@
 };
 extern struct loader_info loader_info;
 
-void start(void *sp);
+void start(void);
 int ft_init(void *dt_blob, unsigned int max_size, unsigned int max_find_device);
 int serial_console_init(void);
 int ns16550_console_init(void *devp, struct serial_console_data *scdp);