of: merge of_attach_node() & of_detach_node()

Merge common code between PowerPC and Microblaze

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Tested-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/prom.h

@@ -34,10 +34,6 @@ extern struct device_node *of_chosen;
 
 #define HAVE_ARCH_DEVTREE_FIXUPS
 
-/* For updating the device tree at runtime */
-extern void of_attach_node(struct device_node *);
-extern void of_detach_node(struct device_node *);
-
 #ifdef CONFIG_PPC32
 /*
  * PCI <-> OF matching functions