The headphone automute on this machine triggers annoying pop noises.
It seems that only the first DAC can be used, the secondary DAC always
results in this problem.  This patch disables the secondary DAC with
a few additional workarounds.
Signed-off-by: Kailang Yang <kailang@realtek.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>