avfilter/vf_zscale: fix output color_range discrepancy

This filter chain was supposed to convert from narrow range
to full range yuv444p, but didn't:

buffer=width=1280:height=720:pix_fmt=yuv444p:frame_rate=25/1:\
time_base=1/25:sar=1/1,zscale=min=709:rin=limited:pin=709:\
tin=709:t=linear,format=gbrpf32le,zscale=tin=linear:p=709:m=709:\
r=full:t=709,format=pix_fmts=yuv444p,buffersink

libavfilter/vf_zscale.c

@@ -676,7 +676,7 @@ static int filter_frame(AVFilterLink *link, AVFrame *in)
         out->color_primaries = (int)s->dst_format.color_primaries;
 
     if (s->range != -1)
-        out->color_range = (int)s->dst_format.pixel_range;
+        out->color_range = (int)s->dst_format.pixel_range + 1;
 
     if (s->trc != -1)
         out->color_trc = (int)s->dst_format.transfer_characteristics;