Renamings for OBMC experiment

To get ready for pulling AV1 to nextgenv2
Replace the experimental flag by MOTION_VAR. Rename major variables.

Change-Id: If6cf4f37b9319c46d8f90df551cc7295d66ca205
diff --git a/aom_dsp/sad.c b/aom_dsp/sad.c
index 7d284fc..2172b6c 100644
--- a/aom_dsp/sad.c
+++ b/aom_dsp/sad.c
@@ -410,7 +410,7 @@
 #endif  // CONFIG_AOM_HIGHBITDEPTH
 #endif  // CONFIG_AV1 && CONFIG_EXT_INTER
 
-#if CONFIG_AV1 && CONFIG_OBMC
+#if CONFIG_AV1 && CONFIG_MOTION_VAR
 // pre: predictor being evaluated
 // wsrc: target weighted prediction (has been *4096 to keep precision)
 // mask: 2d weights (scaled by 4096)
@@ -509,4 +509,4 @@
 HIGHBD_OBMCSADMXN(4, 4)
 /* clang-format on */
 #endif  // CONFIG_AOM_HIGHBITDEPTH
-#endif  // CONFIG_AV1 && CONFIG_OBMC
+#endif  // CONFIG_AV1 && CONFIG_MOTION_VAR