Fix Q register encoding for registers other than Q0. Also, fix value in NeonSize
enumeration.

BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/207523005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20163 ce2b1a6d-e550-0410-aec6-3dcde31c8c00