Declare CopyRow_AVX as using xmm usage, not ymm. Should resolve chromium build error for Android Atom.
BUG=libyuv:369
TESTED=untested
R=tpsiaki@google.com

Review URL: https://webrtc-codereview.appspot.com/31609004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1118 16f28f9a-4ce2-e073-06de-1de4eb20be90