rtc-screen: Enable skip_lf_screen only for sp >= 9

Keep it off at speed < 9 to maintain better
quality at lower speeds.

Change-Id: I13dff1656a6c5ebb44e640a42d2e72566d3c1bab
diff --git a/av1/encoder/speed_features.c b/av1/encoder/speed_features.c
index f4aa5cc..2beaefc 100644
--- a/av1/encoder/speed_features.c
+++ b/av1/encoder/speed_features.c
@@ -1296,7 +1296,7 @@
   }
   if (cpi->oxcf.tune_cfg.content == AOM_CONTENT_SCREEN) {
     if (speed <= 9) sf->rt_sf.use_idtx_nonrd = 1;
-    sf->rt_sf.skip_lf_screen = 1;
+    if (speed >= 9) sf->rt_sf.skip_lf_screen = 1;
     sf->rt_sf.skip_cdef_sb = 1;
     sf->rt_sf.use_rtc_tf = 0;
     sf->rt_sf.use_comp_ref_nonrd = 0;