Clean up shorten-64-to-32 warning in scan.c

Change-Id: Ifbc5310fa6476c64db9d35576fa45dfb2014989f

av1/common/scan.c

diff --git a/av1/common/scan.c b/av1/common/scan.c
index 2377d90..6d0d15e 100644
--- a/av1/common/scan.c
+++ b/av1/common/scan.c
@@ -6600,6 +6600,10 @@
   }
 }
 
+static INLINE int clamp_64(int64_t value, int low, int high) {
+  return value < low ? low : (value > high ? high : (int)value);
+}
+
 static void update_scan_prob(AV1_COMMON *cm, TX_SIZE tx_size, TX_TYPE tx_type,
                              int rate_16) {
   FRAME_CONTEXT *pre_fc = &cm->frame_contexts[cm->frame_context_idx];
@@ -6615,7 +6619,9 @@
     int64_t prev_prob = prev_non_zero_prob[i];
     int64_t pred_prob =
         (curr_prob * rate_16 + prev_prob * ((1 << 16) - rate_16)) >> 16;
-    non_zero_prob[i] = clamp(pred_prob, 0, UINT16_MAX);
+    // TODO(angiebird): reduce the bit usage of probabilities and remove
+    // clamp_64()
+    non_zero_prob[i] = clamp_64(pred_prob, 0, UINT16_MAX);
   }
 }