ARM64: never record safepoint with doubles

R=bmeurer@chromium.org, ulan@chromium.org

BUG=

Review URL: https://codereview.chromium.org/400223002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22498 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Always sweep precisely.

BUG=
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/398013003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22499 ce2b1a6d-e550-0410-aec6-3dcde31c8c00