ALSA: hda - Support VGA-switcheroo

Add the support for VGA-switcheroo in the HD-audio controller side.
When the graphics controller is disabled, the HD-audio driver also delays
the initialization until it's activated by VGA-switcheroo.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=43155Signed-off-by: Takashi Iwai <tiwai@suse.de>