First pass mv_limits setting

Modified mv_limits setting in first pass motion search, making it
consistent with mv_limits in other encoder stages.

Speed 1 borg test result:
        avg_psnr:  ovr_psnr:  ssim:  speed change:
lowres: -0.016	   -0.019    -0.020  -0.1%
midres: -0.043	   -0.043    -0.037   0.1%
Minor impact on quality and speed.

STATS_CHANGED

Change-Id: Ia8315daf39d9ab6695f249dfe5b4d6eb9a475ac0
diff --git a/av1/encoder/firstpass.c b/av1/encoder/firstpass.c
index e2696a7..fd7dcd2 100644
--- a/av1/encoder/firstpass.c
+++ b/av1/encoder/firstpass.c
@@ -424,9 +424,8 @@
 
     // Set up limit values for motion vectors to prevent them extending
     // outside the UMV borders.
-    x->mv_limits.row_min = -((mb_row * 16) + BORDER_MV_PIXELS_B16);
-    x->mv_limits.row_max =
-        ((cm->mb_rows - 1 - mb_row) * 16) + BORDER_MV_PIXELS_B16;
+    av1_set_mv_row_limits(cm, &x->mv_limits, (mb_row << 2),
+                          (16 >> MI_SIZE_LOG2), cpi->oxcf.border_in_pixels);
 
     for (mb_col = 0; mb_col < cm->mb_cols; ++mb_col) {
       int this_intra_error;
@@ -525,9 +524,8 @@
 
       // Set up limit values for motion vectors to prevent them extending
       // outside the UMV borders.
-      x->mv_limits.col_min = -((mb_col * 16) + BORDER_MV_PIXELS_B16);
-      x->mv_limits.col_max =
-          ((cm->mb_cols - 1 - mb_col) * 16) + BORDER_MV_PIXELS_B16;
+      av1_set_mv_col_limits(cm, &x->mv_limits, (mb_col << 2),
+                            (16 >> MI_SIZE_LOG2), cpi->oxcf.border_in_pixels);
 
       if (!frame_is_intra_only(cm)) {  // Do a motion search
         int tmp_err, motion_error, raw_motion_error;
diff --git a/av1/encoder/mcomp.h b/av1/encoder/mcomp.h
index 9d4f372..8a66cf1 100644
--- a/av1/encoder/mcomp.h
+++ b/av1/encoder/mcomp.h
@@ -29,9 +29,6 @@
 #define MAX_FULL_PEL_VAL ((1 << (MAX_MVSEARCH_STEPS - 1)) - 1)
 // Maximum size of the first step in full pel units
 #define MAX_FIRST_STEP (1 << (MAX_MVSEARCH_STEPS - 1))
-// Allowed motion vector pixel distance outside image border
-// for Block_16x16
-#define BORDER_MV_PIXELS_B16 (16 + AOM_INTERP_EXTEND)
 
 #define SEARCH_RANGE_8P 3
 #define SEARCH_GRID_STRIDE_8P (2 * SEARCH_RANGE_8P + 1)