Fixes a decoder bug

The bug was introduced by the commit that added I8X8 intra prediction
mode for inter frames, the decoder was not update to accept the additional
probability update from encoder. This causes the decoder typicall to crash
when encoder sends intra mode probability update.

Change-Id: Ib7dc42dc77a51178aa9ece41e081829818a25016

vp8/decoder/decodemv.c

@@ -490,7 +490,7 @@ static void mb_mode_mv_init(VP8D_COMP *pbi)
             {
                 cm->fc.ymode_prob[i] = (vp8_prob) vp8_read_literal(bc, 8);
             }
-            while (++i < 4);
+            while (++i < VP8_YMODES-1);
         }
 #if CONFIG_UVINTRA
         //vp8_read_bit(bc);
@@ -503,7 +503,7 @@ static void mb_mode_mv_init(VP8D_COMP *pbi)
             {
                 cm->fc.uv_mode_prob[i] = (vp8_prob) vp8_read_literal(bc, 8);
             }
-            while (++i < 3);
+            while (++i < VP8_UV_MODES-1);
         }
 #endif /* CONFIG_UVINTRA */
         read_mvcontexts(bc, mvc);