avformat/mxfenc: Set color siting to 0 for D10-MXF

SMPTE 386M (D-10) lists 4 as value to be used
SMPTE 377-1-2009 says
    "The definitions of 00h (coSiting) and 04h (Rec 601) are equivalent. The value of 04h is deprecated. New
     MXF encoders shall use the value of 00h instead."

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mxfenc.c

@@ -2440,6 +2440,7 @@ static int mxf_write_header(AVFormatContext *s)
                 mxf->edit_unit_byte_count += klv_fill_size(mxf->edit_unit_byte_count);
 
                 sc->signal_standard = 1;
+                sc->color_siting = 0;
             }
             if (mxf->signal_standard >= 0)
                 sc->signal_standard = mxf->signal_standard;