The block level DC_PRED computed by CfL goes down from Q6 to Q0. This
will allow to reuse existing assembly for DC_PRED and also reduce the
requirements on the multilpy required to scale the reconstructed luma
values

Results on Subset1 (compared to f9684d222 with CfL enabled)

   PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
-0.0347 |  0.0229 | -0.1326 |  -0.0420 | -0.0057 | -0.0072 |    -0.0644

Change-Id: I6ba82cc9e04fa4ab7c8ec40a7856deb273881748