Initialize internal buffer pointers in rtc mode

In rtc coding mode, the encoder is running non-RD mode decision. It
does not need dual buffer swap as was the case in the RD mode. This
commit initializes the internal buffer pointers outside the block
coding loop for rtc mode.

Change-Id: Ie076705c60d6b7919217e3f1dfd49e7db5064ac2

vp9/encoder/vp9_onyx_if.c

@@ -1558,6 +1558,7 @@ static void alloc_mode_context(VP9_COMMON *cm, int num_4x4_blk,
   int num_pix = num_4x4_blk << 4;
   int i, k;
   ctx->num_4x4_blk = num_4x4_blk;
+
   CHECK_MEM_ERROR(cm, ctx->zcoeff_blk,
                   vpx_calloc(num_4x4_blk, sizeof(uint8_t)));
   for (i = 0; i < MAX_MB_PLANE; ++i) {
@@ -1601,7 +1602,6 @@ static void init_pick_mode_context(VP9_COMP *cpi) {
   VP9_COMMON *const cm = &cpi->common;
   MACROBLOCK *const x  = &cpi->mb;
 
-
   for (i = 0; i < BLOCK_SIZES; ++i) {
     const int num_4x4_w = num_4x4_blocks_wide_lookup[i];
     const int num_4x4_h = num_4x4_blocks_high_lookup[i];