drm/i915/audio: Introduce a struct for the acomp audio state

Currently we're spreading the stashed state for use of the
audio component hooks all over the place. Start collecting
it up into a single spot.

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/20230124144628.4649-4-ville.syrjala@linux.intel.com