Fix in intra txb hash logic

The index returned by the function find_tx_size_rd_info
was checked for greater than zero which was incorrect.
When tested for 10 frames of parkrun content for speed=1
preset, ~0.6% encode time reduction is seen. BD Rate
improvement of 0.01% is seen in AWCY tests.

STATS_CHANGED

Change-Id: I68b70f572e88976aada8999862e7232de9f7bbdc

av1/encoder/rdopt.c

diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 4d3579d..21c3af5 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -2982,8 +2982,7 @@
     intra_txb_rd_info = &x->txb_rd_record_intra.tx_rd_info[intra_hash_idx];
 
     cur_joint_ctx = (txb_ctx->dc_sign_ctx << 8) + txb_ctx->txb_skip_ctx;
-    if (intra_hash_idx > 0 &&
-        intra_txb_rd_info->entropy_context == cur_joint_ctx &&
+    if (intra_txb_rd_info->entropy_context == cur_joint_ctx &&
         x->txb_rd_record_intra.tx_rd_info[intra_hash_idx].valid) {
       mbmi->txk_type[txk_type_idx] = intra_txb_rd_info->tx_type;
       const TX_TYPE ref_tx_type =