hbd: remove unused variable "use_hbd"

The variable "use_hbd" was defined but not used in four places in the
codebase. The warning that it wasn't used was missed by Jenkins
because it only tries one experimental flag at a time, but these
definitions were inside nested experimental flag conditions. Both
CONFIG_WARPED_MOTION and CONFIG_AOM_HIGHBITDEPTH had to be set for the
variables to be defined.

This patch deletes the unused definitions to remove the unused variable
warnings when the AV1 encoder and/or decoder are built with warped
motion and high bitdepth configured.

Change-Id: I9e80523db05a7a19cebe3ec8085a4a1e4b198c52
diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index e79221a..5af7acd 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -1701,10 +1701,6 @@
 #if CONFIG_WARPED_MOTION
     if (mbmi->motion_mode == WARPED_CAUSAL) {
       int i;
-#if CONFIG_AOM_HIGHBITDEPTH
-      int use_hbd = xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH;
-#endif  // CONFIG_AOM_HIGHBITDEPTH
-
       for (i = 0; i < 3; ++i) {
         const struct macroblockd_plane *pd = &xd->plane[i];
 
diff --git a/av1/encoder/encodeframe.c b/av1/encoder/encodeframe.c
index 065ea0e..2331bd4 100644
--- a/av1/encoder/encodeframe.c
+++ b/av1/encoder/encodeframe.c
@@ -5705,10 +5705,6 @@
 #if CONFIG_WARPED_MOTION
     if (mbmi->motion_mode == WARPED_CAUSAL) {
       int i;
-#if CONFIG_AOM_HIGHBITDEPTH
-      int use_hbd = xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH;
-#endif  // CONFIG_AOM_HIGHBITDEPTH
-
       for (i = 0; i < 3; ++i) {
         const struct macroblockd_plane *pd = &xd->plane[i];
 
diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 24da721..86289a6 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -8810,10 +8810,6 @@
       if (find_projection(mbmi->num_proj_ref[0], pts, pts_inref,
                           &mbmi->wm_params[0], mi_row, mi_col) == 0) {
         int plane;
-#if CONFIG_AOM_HIGHBITDEPTH
-        int use_hbd = xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH;
-#endif  // CONFIG_AOM_HIGHBITDEPTH
-
         for (plane = 0; plane < 3; ++plane) {
           const struct macroblockd_plane *pd = &xd->plane[plane];
 
@@ -10701,12 +10697,9 @@
     if (is_inter_mode(mbmi->mode)) {
 #if CONFIG_WARPED_MOTION
       if (mbmi->motion_mode == WARPED_CAUSAL) {
-        int plane;
-#if CONFIG_AOM_HIGHBITDEPTH
-        int use_hbd = xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH;
-#endif  // CONFIG_AOM_HIGHBITDEPTH
         assert(!has_second_ref(mbmi));
 
+        int plane;
         for (plane = 0; plane < 3; ++plane) {
           const struct macroblockd_plane *pd = &xd->plane[plane];