ALSA: HDA: VIA Add support for codec VT1705CF.

Add support for new codec VT1705CF.
When power on/off Audio output converter of VT1705CF, the stream tag
will be cleared. But driver caches the value. So when power on Audio
output converter, the update_conv_power_state() will restore the saved
stream tag of it.

Signed-off-by: Lydia Wang <lydiawang@viatech.com.cn>
Signed-off-by: Takashi Iwai <tiwai@suse.de>