drm/i915: Restore very early GPU reset

In commit d03b224f ("drm/i915/gt: Apply sanitiization just before
resume") the GT sanitization was pulled into the resume path as we need
to know the backend in order to do a full reset prior to resume.
However, it is still imperative that we scrub existing GPU state before
clobbering in our early setup, so restore a minimal GPU reset at the
start of our init sequence.

Fixes: d03b224f ("drm/i915/gt: Apply sanitiization just before resume")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191228111255.3086901-1-chris@chris-wilson.co.uk