drm/i915: Pass platform device to LPE audio notifier

This allows the LPE HDMI driver to clean up its global variable
reference.

Also drop to pass the eld pointer because the connection status and
the ELD bytes can be retrieved from the attached pdata.

Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>