Useful for verifying our bookkeeper when we encounter is knowing whether
we think the engine is idle at the time of the GPU hang.

References: https://bugs.freedesktop.org/show_bug.cgi?id=104305Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171219131419.13117-1-chris@chris-wilson.co.uk