dxva2: move _WIN32_WINNT handling to public header

This removes duplicate code
Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/dxva2.h

@@ -29,7 +29,14 @@
  * Public libavcodec DXVA2 header.
  */
 
+#if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0600
+#undef _WIN32_WINNT
+#endif
+
+#if !defined(_WIN32_WINNT)
 #define _WIN32_WINNT 0x0600
+#endif
+
 #include <stdint.h>
 #include <d3d9.h>
 #include <dxva2api.h>

libavcodec/dxva2_internal.h

@@ -23,14 +23,6 @@
 #ifndef AVCODEC_DXVA_INTERNAL_H
 #define AVCODEC_DXVA_INTERNAL_H
 
-#if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0600
-#undef _WIN32_WINNT
-#endif
-
-#if !defined(_WIN32_WINNT)
-#define _WIN32_WINNT 0x0600
-#endif
-
 #define COBJMACROS
 
 #include "config.h"