of: protect linux/of.h with CONFIG_OF

For platforms that have CONFIG_OF optional, we need to make the contents
of linux/of.h conditional on CONFIG_OF.
Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Michal Simek <monstr@monstr.eu>

include/linux/of.h

@@ -22,6 +22,8 @@
 
 #include <asm/byteorder.h>
 
+#ifdef CONFIG_OF
+
 typedef u32 phandle;
 typedef u32 ihandle;
 
@@ -194,4 +196,5 @@ extern void of_attach_node(struct device_node *);
 extern void of_detach_node(struct device_node *);
 #endif
 
+#endif /* CONFIG_OF */
 #endif /* _LINUX_OF_H */