proc_devtree: fix THIS_MODULE without module.h

Commit e22f628395 introduced a build
breakage for ARM devtree work: the THIS_MODULE macro was added, but we
don't have module.h

This change adds the necessary #include to get THIS_MODULE defined.
While we could just replace it with NULL (PROC_FS is a bool, not a
tristate), using THIS_MODULE will prevent unexpected breakage if we
ever do compile this as a module.

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>

fs/proc/proc_devtree.c

@@ -11,6 +11,7 @@
 #include <linux/stat.h>
 #include <linux/string.h>
 #include <linux/of.h>
+#include <linux/module.h>
 #include <asm/prom.h>
 #include <asm/uaccess.h>
 #include "internal.h"