MIPS: Remove mterp reliance on code item layout

This is a follow-up to
https://android-review.googlesource.com/529455

Test: ./run-test --interpreter 003-omnibus-opcodes
Test: ./run-test --interpreter 083-compiler-regressions
Test: ./run-test --interpreter --64 003-omnibus-opcodes
Test: ./run-test --interpreter --64 083-compiler-regressions

Change-Id: I72a3f6b0c3583a149db7aa151a79358fe15223b5
8 files changed