[Intel-gfx] Logical (HW) contexts for gen4/gen5

[Chris Wilson]

Since the last posting, the surreptious enabling patch for mesa did
land

commit b5e266765a60aa0f05de646d5580ee8c71156ff1
Author:     Chris Wilson <chris at chris-wilson.co.uk>
AuthorDate: Fri Dec 15 13:42:25 2017 +0000
Commit:     Kenneth Graunke <kenneth at whitecape.org>
CommitDate: Thu May 3 01:39:33 2018 -0700

    i965: Always try to create a logical context

which I suppose I could have taken as an implicit ack for this pair of
patches to enable the logical context support in the kernel as well.
-Chris