Skip intra mode evaluation

Adjusted intra mode masks for y and uv modes at speed 6.
Borg test result at speed 6:
       avg_psnr:  ovr_psnr:  ssim:  encoder speedup:
hdres2:  0.068     0.065     0.006     0.7
Negligible change for midres2.

STATS_CHANGED

Change-Id: I3c7168b1e48fb1896e3619a1eeca49744bca631c
diff --git a/av1/encoder/speed_features.c b/av1/encoder/speed_features.c
index af60a08..4c776bf 100644
--- a/av1/encoder/speed_features.c
+++ b/av1/encoder/speed_features.c
@@ -1006,6 +1006,10 @@
 
     sf->intra_sf.chroma_intra_pruning_with_hog = 4;
     sf->intra_sf.intra_pruning_with_hog = 4;
+    sf->intra_sf.intra_uv_mode_mask[TX_32X32] = UV_INTRA_DC;
+    sf->intra_sf.intra_uv_mode_mask[TX_64X64] = UV_INTRA_DC;
+    sf->intra_sf.intra_y_mode_mask[TX_32X32] = INTRA_DC;
+    sf->intra_sf.intra_y_mode_mask[TX_64X64] = INTRA_DC;
 
     sf->part_sf.prune_rectangular_split_based_on_qidx =
         boosted || allow_screen_content_tools ? 0 : 1;