For reducing the global variable reference, keep snd_intelhad object
in the context and pass it to each helper.  It's a preliminary change
for further cleanup.

This also includes the simplification of the probe procedure: the LPE
platform driver directly gets the created snd_intelhad object by
hdmi_audio_probe(), and passes it to each helper and destructor,
hdmi_audio_remove().  The hdmi_audio_probe() function doesn't call the
back-registration any longer, which is fairly useless.  The LPE
platform driver initializes the stuff instead at the right place, and
calls the wq after the object creation in the probe function itself.
Signed-off-by: Takashi Iwai <tiwai@suse.de>