Revert "Use the same registers for StoreIC and KeyedStoreIC."

This reverts commit r22358 due to release mode arm64 test failures.

TBR=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/385073007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22359 ce2b1a6d-e550-0410-aec6-3dcde31c8c00