[NORMATIVE] Clamp projected mfmv to 15 bits

Clamp the projected mfmv to 15 bits range.

BUG=aomedia:1676

Change-Id: Id29024f51017b2b79d00b52fc6188371feb15d40

av1/common/mvref_common.c

diff --git a/av1/common/mvref_common.c b/av1/common/mvref_common.c
index 00e1120..250d3ec 100644
--- a/av1/common/mvref_common.c
+++ b/av1/common/mvref_common.c
@@ -34,8 +34,10 @@
                 : AOMMAX(num, -MAX_FRAME_DISTANCE);
   int mv_row = ROUND_POWER_OF_TWO_SIGNED(ref.row * num * div_mult[den], 14);
   int mv_col = ROUND_POWER_OF_TWO_SIGNED(ref.col * num * div_mult[den], 14);
-  output->row = (int16_t)clamp(mv_row, INT16_MIN, INT16_MAX);
-  output->col = (int16_t)clamp(mv_col, INT16_MIN, INT16_MAX);
+  const int clamp_max = (1 << 14) - 1;
+  const int clamp_min = -(1 << 14);
+  output->row = (int16_t)clamp(mv_row, clamp_min, clamp_max);
+  output->col = (int16_t)clamp(mv_col, clamp_min, clamp_max);
 }
 
 void av1_copy_frame_mvs(const AV1_COMMON *const cm, MODE_INFO *mi, int mi_row,