Fix incorrect costing for TX_64x64 coefficients

BUG=aomedia:2450

        avg_psnr:	ovr_psnr:	ssim:	psnr_hvs:
lowres:   -0.063	-0.067	        -0.117	-0.087
midres:   -0.033	-0.037	        -0.050	-0.033
hdres:    -0.049	-0.051	        -0.040	-0.046


STATS_CHANGED

Change-Id: I7c5e7587a419a41bb1dbadde354a26f75653bb74
diff --git a/av1/encoder/rd.c b/av1/encoder/rd.c
index 55ba611..ec61406 100644
--- a/av1/encoder/rd.c
+++ b/av1/encoder/rd.c
@@ -549,8 +549,9 @@
         int br_rate[BR_CDF_SIZE];
         int prev_cost = 0;
         int i, j;
-        av1_cost_tokens_from_cdf(br_rate, fc->coeff_br_cdf[tx_size][plane][ctx],
-                                 NULL);
+        av1_cost_tokens_from_cdf(
+            br_rate, fc->coeff_br_cdf[AOMMIN(tx_size, TX_32X32)][plane][ctx],
+            NULL);
         // printf("br_rate: ");
         // for(j = 0; j < BR_CDF_SIZE; j++)
         //  printf("%4d ", br_rate[j]);