ARM64: small fixes for ArgumentAdaptorTrampoline after r20751.

BUG=
R=jacob.bramley@arm.com

Review URL: https://codereview.chromium.org/252483002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20928 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Don't move the object start of objects on non-swept pages.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/255603002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20929 ce2b1a6d-e550-0410-aec6-3dcde31c8c00