drm/i915: Push audio enable/disable further out

Push the audio enable/disable to be the last/first thing
respectively that is done in the encoder enable/disable hooks.
The goal is to move it further out of these encoder hooks entirely.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231121054324.9988-5-ville.syrjala@linux.intel.com