MIPS: Support for super keyed loads where key is a name.

Port r24403 (891eb62)

BUG=v8:3330
LOG=N
R=dusan.milosavljevic@imgtec.com

Review URL: https://codereview.chromium.org/630003002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24422 ce2b1a6d-e550-0410-aec6-3dcde31c8c00