Fix typo in include guard

Change-Id: Iaa321e5cff16a2f814acb9f6b3278e69877a4cab

av1/reference_manager.h

diff --git a/av1/reference_manager.h b/av1/reference_manager.h
index 8a6734f..50c8369 100644
--- a/av1/reference_manager.h
+++ b/av1/reference_manager.h
@@ -9,8 +9,8 @@
  * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
  */
 
-#ifndef AOM_AV1_REFRENCE_MANAGER_H_
-#define AOM_AV1_REFRENCE_MANAGER_H_
+#ifndef AOM_AV1_REFERENCE_MANAGER_H_
+#define AOM_AV1_REFERENCE_MANAGER_H_
 
 #include <deque>
 #include <iostream>
@@ -77,4 +77,4 @@
 
 }  // namespace aom
 
-#endif  // AOM_AV1_REFRENCE_MANAGER_H_
+#endif  // AOM_AV1_REFERENCE_MANAGER_H_