Allow sub8x8 intra modes test for alt frame coding

This commit allows sub8x8 intra modes test in the rate-distortion
loop for hd sequences in speed 1 and 2.

For sequence y90n of hd set at 8000 kbps, speed 2 runtime goes
from 207s to 210s. For ped_1080p at 3000 kbps, speed 2 runtim goes
from 336s to 337s. Both are running with 300 frames.

This improves compression performance by 0.24% for stdhd and 0.32%
for hd.

Change-Id: I173ca38a6411565ae6cfadd184c42b2070c5de1f

vp9/encoder/vp9_onyx_if.c

@@ -791,7 +791,8 @@ void vp9_set_speed_features(VP9_COMP *cpi) {
                                      ? USE_FULL_RD : USE_LARGESTALL);
 
         if (MIN(cpi->common.width, cpi->common.height) >= 720)
-          sf->disable_split_mask = DISABLE_ALL_SPLIT;
+          sf->disable_split_mask = cpi->common.show_frame ?
+              DISABLE_ALL_SPLIT : DISABLE_ALL_INTER_SPLIT;
         else
           sf->disable_split_mask = DISABLE_COMPOUND_SPLIT;
 
@@ -808,10 +809,12 @@ void vp9_set_speed_features(VP9_COMP *cpi) {
                                      ? USE_FULL_RD : USE_LARGESTALL);
 
         if (MIN(cpi->common.width, cpi->common.height) >= 720)
-          sf->disable_split_mask = DISABLE_ALL_SPLIT;
+          sf->disable_split_mask = cpi->common.show_frame ?
+              DISABLE_ALL_SPLIT : DISABLE_ALL_INTER_SPLIT;
         else
           sf->disable_split_mask = LAST_AND_INTRA_SPLIT_ONLY;
 
+
         sf->mode_search_skip_flags = FLAG_SKIP_INTRA_DIRMISMATCH |
                                      FLAG_SKIP_INTRA_BESTINTER |
                                      FLAG_SKIP_COMP_BESTINTRA |