ALSA: hda - Replace bus pm_notify with the standard runtime PM framework

Now the final bit of runtime PM cleanup: instead of manual
notification of the power up/down of the codec via hda_bus pm_notify
ops, use the standard runtime PM feature.

The child codec device will kick off the runtime PM of the parent
(PCI) device upon suspend/resume automatically.  For managing whether
the link can be really turned off, we use the bit flags
bus->codec_powered instead of the earlier bus->power_keep_link_on.
flag.  Each codec driver is responsible to set/clear the bit flag, and
the controller device can be turned off only when all these bits are
cleared.

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