snd/hda, drm/i915: Track the display_power_status using a cookie

drm/i915 is tracking all wakeref owners with a cookie in order to
identify leaks. To that end, each rpm acquisition ops->get_power is
assigned a cookie which should be passed to ops->put_power to signify
its release (and removal from the list of wakeref owners). As snd/hda is
already using a bool to track current status of display_power extending
that to an unsigned long to hold the boolean cookie is a trivial
extension, and will quell all doubt that snd/hda is the cause of the
device runtime pm leaks.

v2: Keep using the power abstraction for local wakeref tracking.
v3: BUILD_BUG_ON impedance mismatch

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Jani Nikula <jani.nikula@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190213152109.16997-1-chris@chris-wilson.co.uk