ALSA: hda - Make sure mute LEDs stay on during runtime suspend (Realtek)

commit d5b6b65e75ce607c2734227524e11574317a1c1a upstream.

Some HP machines with Realtek codecs have mute LEDs connected to VREF pins.
However when these go into runtime suspend, the pin powers down and its
pin control is disabled, thus disabling the LED too.

This patch fixes that issue by making sure that the pin stays in D0 with
correct pin control.

BugLink: https://bugs.launchpad.net/bugs/1248465


Tested-by: Franz Hsieh <franz.hsieh@canonical.com>
Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>