MIPS: Use LookupIterator for CompileLoadInterceptor and delete Object::Lookup.

Port r23168 (d860963)

BUG=
R=akos.palfi@imgtec.com

Review URL: https://codereview.chromium.org/473243003

Patch from Balazs Kilvady <balazs.kilvady@imgtec.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23173 ce2b1a6d-e550-0410-aec6-3dcde31c8c00