Change r9 to a parameter which will map to x9 for arm64.
BUG=319
TESTED=untested
R=thorcarpenter@google.com, tpsiaki@google.com

Review URL: https://webrtc-codereview.appspot.com/11139004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@998 16f28f9a-4ce2-e073-06de-1de4eb20be90
3 files changed