Remove encoder speed 8 in AV1

Speed 8 called rd_use_partition(), that was from VP9 and was not well
maintained. This patch removed speed 8 in av1 and the unit test.

BUG=aomedia:478

Change-Id: I1379b0327c0283a096680607de0e2b774cea88d0

av1/encoder/speed_features.c

diff --git a/av1/encoder/speed_features.c b/av1/encoder/speed_features.c
index 89d2f50..c638d03 100644
--- a/av1/encoder/speed_features.c
+++ b/av1/encoder/speed_features.c
@@ -271,13 +271,6 @@
     sf->coeff_prob_appx_step = 4;
     sf->mode_search_skip_flags |= FLAG_SKIP_INTRA_DIRMISMATCH;
   }
-  if (speed >= 8) {
-    sf->mv.search_method = FAST_DIAMOND;
-    sf->partition_search_type = VAR_BASED_PARTITION;
-    sf->mv.fullpel_search_step_param = 10;
-    sf->mv.subpel_force_stop = 2;
-    sf->lpf_pick = LPF_PICK_MINIMAL_LPF;
-  }
 }
 
 void av1_set_speed_features_framesize_dependent(AV1_COMP *cpi) {

test/motion_vector_test.cc

diff --git a/test/motion_vector_test.cc b/test/motion_vector_test.cc
index 2830a0b..403a8f1 100644
--- a/test/motion_vector_test.cc
+++ b/test/motion_vector_test.cc
@@ -32,7 +32,7 @@
 };
 
 // Encoding speeds
-const int kCpuUsedVectors[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8 };
+const int kCpuUsedVectors[] = { 0, 1, 2, 3, 4, 5, 6, 7 };
 
 // MV test modes: 1 - always use maximum MV; 2 - always use minimum MV.
 const int kMVTestModes[] = { MAX_EXTREME_MV, MIN_EXTREME_MV };