Move AVX code to conditionals used for AVX2 to require newer compiler.
BUG=367
TESTED=try bots
R=harryjin@google.com

Review URL: https://webrtc-codereview.appspot.com/24819004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1105 16f28f9a-4ce2-e073-06de-1de4eb20be90
3 files changed