Like the previous transition of suspend/resume, now move the
power-save code to the standard runtime PM.  As usual for runtime PM,
it's a bit tricky, but this simplified codes a lot in the end.

For keeping the usage compatibility, power_save module option still
controls the whole power-saving behavior on all codecs.  The value is
translated to pm_runtime_*_autosuspend() and pm_runtime_allow() /
pm_runtime_forbid() calls.

snd_hda_power_up() and snd_hda_power_down() are translated to
pm_runtime_get_sync() and pm_runtime_put_autosuspend(), respectively.
Since we can do call pm_runtime_get_sync() more reliably, the sync
version is used always and snd_hda_power_up_d3wait() is dropped.
Another slight difference is that snd_hda_power_up()/down() don't call
runtime_pm code during the suspend/resume transition phase.  Calling
them there isn't safe unlike our own code, resulted in unexpected
behavior (endless wakeups).

The hda_power_count tracepoint was removed, as it doesn't match well
with the new code.

Last but not least, we need to set ignore_children flag in the parent
dev.power field so that the runtime PM of the controller chip won't
get confused.  The notification is still done in the bus pm_notify
callback.  We'll get rid of this hack in the later patch.

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