ALSA: hda - VIA: Fix side channel mute invalid issue

Modify side_mute_channel() and update_side_mute_status() functions
to fix invalid side channel mute issue of VT2002P, VT1812 and VT1802
codecs.

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