Apply branch prediction on quantize/quantize_skip functions

- On E5-2680, park_joy_1080p, 5 frames, baseline encoding time
  reduces about 0.8~1.0%.
- Credit goes to Erik Niemeyer (erik.a.niemeyer@intel.com).

Change-Id: I69f191d5a4e4b96a5f9ffd8286e484b69d565c01
1 file changed