MIPS: Keyed stores to super where key is a name.

Port r24490 (839f44c)

BUG=v:3330
LOG=N
R=paul.lind@imgtec.com

Review URL: https://codereview.chromium.org/641093002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24501 ce2b1a6d-e550-0410-aec6-3dcde31c8c00