ALSA: x86: Flatten two abstraction layers

This is the final stage for a big clean-up series.  Here we flatten
the two layers into one.  Formerly, the implementation was split to
HDMI "shell" that talks with the platform device, and HDMI audio part
that communicates via caps and other event handlers.  All these would
be good if there were multiple instantiations or if there were data
protection.  But neither are true in our case.  That said, it'll be
easier to have a flat driver structure in the end.

In this patch, the former struct hdmi_lpe_audio_ctx is forged into the
existing struct snd_intelhad.  The latter has already a few members
that are basically the copy from the former.  Only a few new members
for the lowlevel I/O are added by this change.

Then, the had_get_caps() and had_set_caps() are simply replaced with
the direct calls to copy the data in the struct fields.  Also, the
had_event_handler() calls are replaced with the direct call for each
event as well.

Signed-off-by: Takashi Iwai <tiwai@suse.de>