Speed up tm_predictor_8x8
Speed up tm_predictor_8x8

Left neighbor read from memory only once.
Speed up by ~20% in ./test_intra_pred_speed.

Change-Id: Ia1388630df6fed0dce9a6eeded6cb855bbc43505

luctrudeau/aom,jmvalin/aom,smarter/aom,mbebenita/aom,ShiftMediaProject/libvpx,ittiamvpx/libvpx-1,thdav/aom,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,openpeer/libvpx_new,mwgoldsmith/libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,jmvalin/aom,webmproject/libvpx,thdav/aom,mbebenita/aom,mbebenita/aom,webmproject/libvpx,ittiamvpx/libvpx-1,luctrudeau/aom,mbebenita/aom,thdav/aom,thdav/aom,smarter/aom,smarter/aom,luctrudeau/aom,Topopiccione/libvpx,mwgoldsmith/vpx,GrokImageCompression/aom,Topopiccione/libvpx,ShiftMediaProject/libvpx,openpeer/libvpx_new,mwgoldsmith/libvpx,ittiamvpx/libvpx-1,ittiamvpx/libvpx-1,mwgoldsmith/vpx,GrokImageCompression/aom,Topopiccione/libvpx,ittiamvpx/libvpx-1,jmvalin/aom,GrokImageCompression/aom,openpeer/libvpx_new,GrokImageCompression/aom,shacklettbp/aom,ShiftMediaProject/libvpx,mbebenita/aom,shacklettbp/aom,mbebenita/aom,luctrudeau/aom,Topopiccione/libvpx,shacklettbp/aom,jmvalin/aom,mbebenita/aom,ShiftMediaProject/libvpx,mbebenita/aom,openpeer/libvpx_new,Topopiccione/libvpx,webmproject/libvpx,smarter/aom,ittiamvpx/libvpx-1,jmvalin/aom,shacklettbp/aom,GrokImageCompression/aom,mwgoldsmith/vpx,openpeer/libvpx_new,smarter/aom,mwgoldsmith/vpx,thdav/aom,GrokImageCompression/aom,mwgoldsmith/vpx,openpeer/libvpx_new,Topopiccione/libvpx,shacklettbp/aom,jmvalin/aom,luctrudeau/aom,shacklettbp/aom,luctrudeau/aom,webmproject/libvpx,mbebenita/aom,mwgoldsmith/libvpx,thdav/aom,smarter/aom,mwgoldsmith/libvpx,mwgoldsmith/libvpx