configure: Add missing identity filter->scene_sad dependency

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

configure

@@ -3861,6 +3861,7 @@ histeq_filter_deps="gpl"
 hqdn3d_filter_deps="gpl"
 iccdetect_filter_deps="lcms2"
 iccgen_filter_deps="lcms2"
+identity_filter_select="scene_sad"
 interlace_filter_deps="gpl"
 kerndeint_filter_deps="gpl"
 ladspa_filter_deps="ladspa libdl"