[arm] Add support for ROR. Refactor operand2 handling.

This was the last missing bit for full "flexible second operand" /
operand2 support on ARM.

TEST=cctest/test-instruction-selector-arm,cctest/test-run-machops
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/434553002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22732 ce2b1a6d-e550-0410-aec6-3dcde31c8c00