Flatten nmv context model

The nmv context model dependency on the reconstructed mvs has been
deprecated. This commit converts the nmv context model to scalar
case.

Change-Id: I27f45b9d16b0e4ebdde10abd17dba873ccf6b138
diff --git a/av1/encoder/block.h b/av1/encoder/block.h
index f7e7b98..26a827b 100644
--- a/av1/encoder/block.h
+++ b/av1/encoder/block.h
@@ -205,10 +205,10 @@
   int pred_mv_sad[TOTAL_REFS_PER_FRAME];
 
   int *nmvjointcost;
-  int nmv_vec_cost[NMV_CONTEXTS][MV_JOINTS];
-  int *nmvcost[NMV_CONTEXTS][2];
-  int *nmvcost_hp[NMV_CONTEXTS][2];
-  int **mv_cost_stack[NMV_CONTEXTS];
+  int nmv_vec_cost[MV_JOINTS];
+  int *nmvcost[2];
+  int *nmvcost_hp[2];
+  int **mv_cost_stack;
   int **mvcost;
 
   int32_t *wsrc_buf;