Refactor temporal MV code

Removed rounding of blk_row/blk_col, which is more clear and doesn't
change the result since the step size(mi_step) are even number.

Change-Id: I3b0de69316e10c4834eb2d0d7e160a0ec9fbf130

av1/common/mvref_common.c

diff --git a/av1/common/mvref_common.c b/av1/common/mvref_common.c
index ef16e02..7f9ca1d 100644
--- a/av1/common/mvref_common.c
+++ b/av1/common/mvref_common.c
@@ -585,8 +585,8 @@
                           CANDIDATE_MV *ref_mv_stack, int16_t *mode_context) {
 #if CONFIG_TMV
   const MV_REF *prev_frame_mvs = prev_frame_mvs_base +
-                                 ((blk_row + 1) >> 1) * prev_frame_mvs_stride +
-                                 ((blk_col + 1) >> 1);
+                                 (blk_row >> 1) * prev_frame_mvs_stride +
+                                 (blk_col >> 1);
 #else
   const MV_REF *prev_frame_mvs =
       prev_frame_mvs_base + blk_row * prev_frame_mvs_stride + blk_col;

av1/decoder/decodemv.c

diff --git a/av1/decoder/decodemv.c b/av1/decoder/decodemv.c
index cac27e9..1b69c48 100644
--- a/av1/decoder/decodemv.c
+++ b/av1/decoder/decodemv.c
@@ -3063,9 +3063,8 @@
                                      int mi_col, int x_mis, int y_mis) {
 #if CONFIG_TMV
   const int frame_mvs_stride = ROUND_POWER_OF_TWO(cm->mi_cols, 1);
-  MV_REF *frame_mvs = cm->cur_frame->mvs +
-                      ((mi_row & 0xfffe) >> 1) * frame_mvs_stride +
-                      ((mi_col & 0xfffe) >> 1);
+  MV_REF *frame_mvs =
+      cm->cur_frame->mvs + (mi_row >> 1) * frame_mvs_stride + (mi_col >> 1);
   x_mis = ROUND_POWER_OF_TWO(x_mis, 1);
   y_mis = ROUND_POWER_OF_TWO(y_mis, 1);
 #else