ALSA: hda - Fix S3/S4 problem on machines with VREF-pin mute-LED

The verb command in stac92xx_post_suspend caused the audio to stop
working after resuming from S3 mode on HP laptops with the VREF-pin
mute-LED control.  Removing relevant post_suspend registering.

Although removing D3 on AFG is no optimal solution, the impact should
be small in comparison with the broken S3/S4.

Signed-off-by: Charles Chin <Charles.Chin@idt.com>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>