[turbofan] Tests and fixes for ARM64 load/store with immediate offset.

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

Review URL: https://codereview.chromium.org/550113002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23906 ce2b1a6d-e550-0410-aec6-3dcde31c8c00