MIPS: Remove BaseLoad/StoreStub compilers, and the stub-cache interface duplication.

Port r17165 (e3cb6e2e)

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/26883007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17172 ce2b1a6d-e550-0410-aec6-3dcde31c8c00