Add use_svc condition to the scene detection in 1 pass.

Scene detection is not currently used in SVC 1 pass code.
Speedup of ~0.4%.

Change-Id: I0ab769300919de710cd2da1402014fa3f22a1f86

vp9/encoder/vp9_encoder.c

@@ -3529,7 +3529,7 @@ static void encode_without_recode_loop(VP9_COMP *cpi, size_t *size,
   if (cpi->compute_source_sad_onepass &&
       (cpi->oxcf.rc_mode == VPX_VBR ||
        cpi->oxcf.content == VP9E_CONTENT_SCREEN ||
-       (cpi->oxcf.speed >= 5 && cpi->oxcf.speed < 8)))
+       (cpi->oxcf.speed >= 5 && cpi->oxcf.speed < 8 && !cpi->use_svc)))
     vp9_scene_detection_onepass(cpi);
 
   // For 1 pass CBR SVC, only ZEROMV is allowed for spatial reference frame