Fix bug in round shift array unit test

According to AV1 decoder specification (section 7.13.3) round shift value can not be negative.
Range of row shift: 0 to 2
Range of column shift: 0 to 4
Thus unit test case is corrected with valid range of bit shift values.
BUG=aomedia:1960

Change-Id: I2c9f67a9c7577b53f0574434ab4171e75144080c

av1/common/av1_txfm.c

diff --git a/av1/common/av1_txfm.c b/av1/common/av1_txfm.c
index 1e66541..5a16209 100644
--- a/av1/common/av1_txfm.c
+++ b/av1/common/av1_txfm.c
@@ -69,19 +69,12 @@
 
 void av1_round_shift_array_c(int32_t *arr, int size, int bit) {
   int i;
-  if (bit == 0) {
-    return;
-  } else {
-    if (bit > 0) {
-      for (i = 0; i < size; i++) {
-        arr[i] = round_shift(arr[i], bit);
-      }
-    } else {
-      for (i = 0; i < size; i++) {
-        arr[i] = (int32_t)clamp64(((int64_t)1 << (-bit)) * arr[i], INT32_MIN,
-                                  INT32_MAX);
-      }
-    }
+  // Bit range is specified in section 7.13.3
+  assert(bit >= 0);
+  assert(bit <= 4);
+  if (bit == 0) return;
+  for (i = 0; i < size; i++) {
+    arr[i] = round_shift(arr[i], bit);
   }
 }
 

test/av1_round_shift_array_test.cc

diff --git a/test/av1_round_shift_array_test.cc b/test/av1_round_shift_array_test.cc
index 825d134..394fda6 100644
--- a/test/av1_round_shift_array_test.cc
+++ b/test/av1_round_shift_array_test.cc
@@ -28,7 +28,7 @@
 typedef void (*comp_round_shift_array_func)(int32_t *arr, int size, int bit);
 
 const int kValidBitCheck[] = {
-  -4, -3, -2, -1, 0, 1, 2, 3, 4,
+  0, 1, 2, 3, 4,
 };
 
 typedef ::testing::tuple<comp_round_shift_array_func, BLOCK_SIZE, int>