dnxhdenc: Replace a forward declaration by the proper #include.

libavcodec/dnxhdenc.c

@@ -28,6 +28,7 @@
 #include "avcodec.h"
 #include "dsputil.h"
 #include "mpegvideo.h"
+#include "mpegvideo_common.h"
 #include "dnxhdenc.h"
 
 #define VE AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
@@ -38,8 +39,6 @@ static const AVOption options[]={
 };
 static const AVClass class = { "dnxhd", av_default_item_name, options, LIBAVUTIL_VERSION_INT };
 
-int dct_quantize_c(MpegEncContext *s, DCTELEM *block, int n, int qscale, int *overflow);
-
 #define LAMBDA_FRAC_BITS 10
 
 static av_always_inline void dnxhd_get_pixels_8x4(DCTELEM *restrict block, const uint8_t *pixels, int line_size)