ALSA: hda - VIA: Fix stereo mixer recording no sound issue

Modify function via_mux_enum_put() to fix stereo mixer recording
no sound issue.

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