Add missing #include guard in xlat_tables.h

Change-Id: I7272a800accb7de71cbbf6b715a43061bbf79f8c
diff --git a/include/aarch64/xlat_tables.h b/include/aarch64/xlat_tables.h
index f7b7740..01b1afe 100644
--- a/include/aarch64/xlat_tables.h
+++ b/include/aarch64/xlat_tables.h
@@ -28,6 +28,9 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#ifndef __XLAT_TABLES_H__
+#define __XLAT_TABLES_H__
+
 #include <stdint.h>
 
 /*
@@ -64,3 +67,5 @@
 extern void init_xlat_tables(void);
 
 extern uint64_t l1_xlation_table[];
+
+#endif /* __XLAT_TABLES_H__ */