lavc: Consistently prefix input buffer defines

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

libavformat/mxg.c

@@ -110,7 +110,7 @@ static int mxg_update_cache(AVFormatContext *s, unsigned int cache_size)
     if (mxg->soi_ptr) soi_pos = mxg->soi_ptr - mxg->buffer;
     mxg->buffer = av_fast_realloc(mxg->buffer, &mxg->buffer_size,
                                   current_pos + cache_size +
-                                  FF_INPUT_BUFFER_PADDING_SIZE);
+                                  AV_INPUT_BUFFER_PADDING_SIZE);
     if (!mxg->buffer)
         return AVERROR(ENOMEM);
     mxg->buffer_ptr = mxg->buffer + current_pos;