MIPS: Revert 21774: "Generate KeyedLoadGeneric with Hydrogen"

Port r21776 (10a4872)

Original commit message:
Due to arm64 and GCMole failures

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/329723007

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21777 ce2b1a6d-e550-0410-aec6-3dcde31c8c00