Also fix mjsunit/regress/regress-undefined-nan to ensure that we are
testing transfer via xmm registers by forcing the transfer to be in an
optimized function.

BUG=v8:3839
LOG=n
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/863153002

Cr-Commit-Position: refs/heads/master@{#26213}