avcodec/exif: don't expose a private function in an installed header

And it doesn't need an entry in APIChanges, given it's not public API.

Signed-off-by: James Almer <jamrial@gmail.com>

doc/APIchanges

@@ -13,8 +13,6 @@ API changes, most recent first:
      av_exif_ifd_to_dict, av_exif_clone_ifd,
      av_exif_matrix_to_orientation,
      av_exif_orientation_to_matrix,
-  Deprecate:
-   - avpriv_exif_decode_ifd (deprecated behind FF_API_OLD_EXIF)
 
 2025-08-19 - bb90b262d6d - lavu 60.10.100 - frame.h
   Add AV_FRAME_DATA_EXIF.

libavcodec/exif.h

@@ -223,10 +223,4 @@ int av_exif_matrix_to_orientation(const int32_t *matrix);
  */
 int av_exif_orientation_to_matrix(int32_t *matrix, int orientation);
 
-#if FF_API_OLD_EXIF
-/* Used by the AVI demuxer */
-int avpriv_exif_decode_ifd(void *logctx, const uint8_t *buf, int size,
-                           int le, int depth, AVDictionary **metadata);
-#endif /* FF_API_OLD_EXIF */
-
 #endif /* AVCODEC_EXIF_H */

libavcodec/exif_internal.h

@@ -34,6 +34,13 @@
 #include "libavutil/frame.h"
 
 #include "exif.h"
+#include "version_major.h"
+
+#if FF_API_OLD_EXIF
+/* Used by the AVI demuxer */
+int avpriv_exif_decode_ifd(void *logctx, const uint8_t *buf, int size,
+                           int le, int depth, AVDictionary **metadata);
+#endif /* FF_API_OLD_EXIF */
 
 /**
  * Attach the data buffer to the frame. This is mostly a wrapper for