a few clean-ups

1. remove prediction mode conversion
2. unified bmode, same for key and non-key frame
3. set I4X4_PRED count for pdf to 0, as I4X4_PRED is no longer
coded ever. It is determined by ref_frame and block partition

Change-Id: If5b282957c24339b241acdb9f2afef85658fe47d

vp9/encoder/vp9_encodeintra.c

@@ -31,8 +31,9 @@ int vp9_encode_intra(VP9_COMP *cpi, MACROBLOCK *x, int use_16x16_pred) {
   } else {
     int i;
 
-    for (i = 0; i < 16; i++)
+    for (i = 0; i < 16; i++) {
       encode_intra4x4block(x, i, BLOCK_SIZE_MB16X16);
+    }
   }
 
   return vp9_get_mb_ss(x->plane[0].src_diff);