proc_devtree: include linux/of.h

Currenly, proc_devtree.c depends on asm/prom.h to include linux/of.h, to
provide some device-tree definitions (eg, struct property).

Instead, include linux/of.h directly. We still need asm/prom.h for
HAVE_ARCH_DEVTREE_FIXUPS.
Signed-off-by: NJeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

fs/proc/proc_devtree.c

@@ -10,6 +10,7 @@
 #include <linux/seq_file.h>
 #include <linux/stat.h>
 #include <linux/string.h>
+#include <linux/of.h>
 #include <asm/prom.h>
 #include <asm/uaccess.h>
 #include "internal.h"