lv_map_multi: make entropy consistent

BUG=aomedia:1060

Change-Id: I051ff95b411cb27b0025cd634b5c599199ed082d

aom_dsp/entdec.c

@@ -157,6 +157,7 @@ int od_ec_decode_bool_q15(od_ec_dec *dec, unsigned f) {
   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

@@ -190,6 +190,7 @@ void od_ec_encode_bool_q15(od_ec_enc *enc, int val, unsigned f) {
   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);