Remove alignment from loops.  Newer cpus will execute the loop efficiently without alignment, and the extra nops would slow the initial iteration marginally if anything.
BUG=none
TESTED=try bots
R=harryjin@google.com

Review URL: https://webrtc-codereview.appspot.com/27199004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1167 16f28f9a-4ce2-e073-06de-1de4eb20be90