drm/i915: Always try to reset the GPU on takeover

When we first introduced the reset to sanitize the GPU on taking over
from the BIOS and before returning control to third parties (the BIOS!),
we restricted it to only systems utilizing HW contexts as we were
uncertain of how stable our reset mechanism truly was. We now have
reasonable coverage across all machines that expose a GPU reset method,
and so we should be safe to sanitize the GPU state everywhere.

v2: We _have_ to skip the reset if it would clobber the display.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190103112104.19561-1-chris@chris-wilson.co.uk