ALSA: hda - Add missing mux check for VT1708

In patch_vt1708(), the check of MUX nids is missing and this results in
the -EINVAL error in accessing Input Source mixer element.  Simpliy
adding the call of get_mux_nids() fixes the problem.

Reference: Novell bnc#534904
	https://bugzilla.novell.com/show_bug.cgi?id=534904Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/hda/patch_via.c

@@ -1395,6 +1395,7 @@ static int patch_vt1708(struct hda_codec *codec)
 	if (!spec->adc_nids && spec->input_mux) {
 		spec->adc_nids = vt1708_adc_nids;
 		spec->num_adc_nids = ARRAY_SIZE(vt1708_adc_nids);
+		get_mux_nids(codec);
 		spec->mixers[spec->num_mixers] = vt1708_capture_mixer;
 		spec->num_mixers++;
 	}