Make omxtypes.h utf-8

Otherwise, Visual Studio warns:

c:\src\cr\src\third_party\openmax_dl\dl\api\omxtypes.h: warning C4828: The file contains a character starting at offset 0x70 that is illegal in the current source character set (codepage 65001).

when building with the /utf8 flag.

R=rtoy@google.com, rtoy@chromium.org
BUG=454858, 637203

Review URL: https://codereview.webrtc.org/2485303002 .

dl/api/omxtypes.h

diff --git a/dl/api/omxtypes.h b/dl/api/omxtypes.h
index b64e779..a244bad 100644
--- a/dl/api/omxtypes.h
+++ b/dl/api/omxtypes.h
@@ -2,7 +2,7 @@
  * File: omxtypes.h
  * Brief: Defines basic Data types used in OpenMAX v1.0.2 header files.
  *
- * Copyright © 2005-2008 The Khronos Group Inc. All Rights Reserved. 
+ * Copyright © 2005-2008 The Khronos Group Inc. All Rights Reserved. 
  *
  * These materials are protected by copyright laws and contain material 
  * proprietary to the Khronos Group, Inc.  You may use these materials