lv_map_multi: make entropy consistent

BUG=aomedia:1060

Change-Id: I051ff95b411cb27b0025cd634b5c599199ed082d

aom_dsp/entdec.c

diff --git a/aom_dsp/entdec.c b/aom_dsp/entdec.c
index ba31710..569cef0 100644
--- a/aom_dsp/entdec.c
+++ b/aom_dsp/entdec.c
@@ -157,6 +157,7 @@
   OD_ASSERT(dif >> (OD_EC_WINDOW_SIZE - 16) < r);
   OD_ASSERT(32768U <= r);
   v = ((r >> 8) * (uint32_t)(f >> EC_PROB_SHIFT) >> (7 - EC_PROB_SHIFT));
+  v += EC_MIN_PROB;
   vw = (od_ec_window)v << (OD_EC_WINDOW_SIZE - 16);
   ret = 1;
   r_new = v;

aom_dsp/entenc.c

diff --git a/aom_dsp/entenc.c b/aom_dsp/entenc.c
index 751235f..8e48b9e 100644
--- a/aom_dsp/entenc.c
+++ b/aom_dsp/entenc.c
@@ -190,6 +190,7 @@
   r = enc->rng;
   OD_ASSERT(32768U <= r);
   v = ((r >> 8) * (uint32_t)(f >> EC_PROB_SHIFT) >> (7 - EC_PROB_SHIFT));
+  v += EC_MIN_PROB;
   if (val) l += r - v;
   r = val ? v : r - v;
   od_ec_enc_normalize(enc, l, r);