drm/i915/audio: Do the vblank waits

drm/i915/audio: Do the vblank waits

The spec tells us to do a bunch of vblank waits in the audio
enable/disable sequences. Make it so.

The FIXMEs are nonsense since we do the audio disable very
early and enable very late, so vblank interrupts are in fact
enabled when we do this.

TODO not sure we actually want these since we don't even rely
on the hw ELD buffer, and these might be there just to give
the audio side a bit of time to respond to the unsol events.
OTOH they might be really needed for some other reason.

Cc: Chaitanya Kumar Borah <[email protected]>
Cc: Kai Vehmanen <[email protected]>
Cc: Takashi Iwai <[email protected]>
Acked-by: Jani Nikula <[email protected]>
Reviewed-by: Kai Vehmanen <[email protected]>
Signed-off-by: Ville Syrjälä <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]