ALSA: hda/realtek - Improve HP depop when system change power state on Chromebook

It is better to change Mic2-Vref to manual mode.
Manual control Mic2-Vref will solve pop noise issue.
It will improve pop noise for power on, power off, S3 and resume.

Signed-off-by: Kailang Yang <kailang@realtek.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>