drm/i915: Call audio pin/ELD notify function

When the audio codec is enabled or disabled, notify the audio driver.
This will enable the audio driver to get the notification at all times
(even when audio is in different powersave states).

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Takashi Iwai <tiwai@suse.de>