Revert "drm/i915/gem: Delete unused code"

These commits caused a regression on Lenovo t520 sandybridge
machine belonging to reporter. We are reverting them for 5.10
for other reasons, so just do it for 5.9 as well.

This reverts commit 7ac2d253.

Reported-by: Harald Arnesen <harald@skogtun.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>