Use the same registers for StoreIC and KeyedStoreIC.

The x64 and ia32 platforms already did this, port to arm and arm64.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/385553004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22358 ce2b1a6d-e550-0410-aec6-3dcde31c8c00