MIPS: Replace HCheckPrototypeMaps by explicit map checks of constant values.

Port r16055 (7567e57f)

BUG=

Review URL: https://codereview.chromium.org/21639003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16060 ce2b1a6d-e550-0410-aec6-3dcde31c8c00