drm/i915/audio: Don't program the hardware ELD buffer on ilk+

drm/i915/audio: Don't program the hardware ELD buffer on ilk+

Since we use the audio component to transfer the ELD to the audio
driver on ilk+ platforms there is no point in even programming
the hardware ELD buffer. Stop doing so.

The one slight caveat here is that this is not strictly legal
according to the HDA spec. PD=1;ELD=0 is only documented as
an intermediate state during modeset. But if there is no hardware
that depends on that then I guess we're fine. Or we could
perhaps set ELD=1 without actually programming the buffer?

Note that the bspec sequence of PD=0;ELD=0 -> PD=1;ELD=0 ->
PD=1;ELD=1 is also not strictly correct according to the HDA
spec, as the only documented transition from PD=0;ELD=0 is
straight to PD=1;ELD=1. But that is not even possible on
these platforms as the bits live in different registers.

Cc: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Cc: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230124144628.4649-2-ville.syrjala@linux.intel.com