av1_txfm,round_shift: remove implicit conv warning

under visual studio c4334:
result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift
intended?)

Change-Id: If06793116ddfbe3265a17a17a2bcaa6ee8cf9e2d

av1/common/av1_txfm.h

diff --git a/av1/common/av1_txfm.h b/av1/common/av1_txfm.h
index 0530b3c..e4c5ae7 100644
--- a/av1/common/av1_txfm.h
+++ b/av1/common/av1_txfm.h
@@ -81,7 +81,7 @@
 
 static INLINE int32_t round_shift(int32_t value, int bit) {
   assert(bit >= 1);
-  return (int32_t)(((int64_t)value + (1 << (bit - 1))) >> bit);
+  return (int32_t)(((int64_t)value + (1ll << (bit - 1))) >> bit);
 }
 
 static INLINE void round_shift_array(int32_t *arr, int size, int bit) {