MIPS: Flesh out vector ic state query and set mechanisms.

Port c142994f742b52cd59aa15d0961d4b0034bcbf88

Original commit message:
The IC system now fully integrates the vector concept and can
handle loads and keyed loads vector-based.

BUG=
R=akos.palfi@imgtec.com

Review URL: https://codereview.chromium.org/752553005

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

Cr-Commit-Position: refs/heads/master@{#25554}