drm/i915: Don't wake the device up to check if the engine is asleep

drm/i915: Don't wake the device up to check if the engine is asleep

If the entire device is powered off, we can safely assume that the
engine is also asleep (and idle).

Reported-by: Tvrtko Ursulin <[email protected]>
Fixes: a091d4ee931b ("drm/i915: Hold a wakeref for probing the ring registers")
Signed-off-by: Chris Wilson <[email protected]>
Cc: Tvrtko Ursulin <[email protected]>
Cc: Mika Kuoppala <[email protected]>
Reviewed-by: Mika Kuoppala <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]