ALSA: x86: Clear the pdata.notify_lpe_audio pointer before teardown

ALSA: x86: Clear the pdata.notify_lpe_audio pointer before teardown

commit 8d5c30308d7c5a17db96fa5452c0232f633377c2 upstream.

Clear the notify function pointer in the platform data before we tear
down the driver. Otherwise i915 would end up calling a stale function
pointer and possibly explode.

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-3-ville.syrjala@linux.intel.com
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>