avformat/matroskaenc: Simplify writing buffer

If one already has the contents of a master elements in a buffer of
known size, then writing a EBML master element is no different from
writing an EBML binary element. It is overtly complicated to use
start/end_ebml_master() as these functions first write an unkown-length
size field of the appropriate length, then write the buffer's contents,
followed by a seek to the length field to overwrite it with the real
size (obtained via avio_tell() although it was already known in
advance), followed by another seek to the previous position. Just use
put_ebml_binary() instead.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavformat/matroskaenc.c

@@ -893,9 +893,7 @@ static void mkv_write_video_color(AVIOContext *pb, const AVCodecParameters *par,
 
     colorinfo_size = avio_tell(dyn_cp);
     if (colorinfo_size) {
-        ebml_master colorinfo = start_ebml_master(pb, MATROSKA_ID_VIDEOCOLOR, colorinfo_size);
-        avio_write(pb, colour, colorinfo_size);
-        end_ebml_master(pb, colorinfo);
+        put_ebml_binary(pb, MATROSKA_ID_VIDEOCOLOR, colour, colorinfo_size);
     }
 }