Avoid out of range

Change-Id: Ia06a6f2ac6473f10f09df3c0cc9cd45c2b781146
diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 7734d59..287c521 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -4614,7 +4614,7 @@
             const int16_t *cur_diff_row = diff + (row + i) * diff_stride + col;
             for (int j = 0; j < cur_tx_bw; j++) {
               hash = hash ^ clip_pixel(cur_diff_row[j] + 128);
-              hash *= 16777619;
+              hash = (uint32_t)((int64_t)hash * 16777619);
             }
           }