ALSA: hda - Don't query connections for widgets have no connections

Fixes the kernel warnings with IDT codecs like
    hda_codec: connection list not available for 0x1e
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/hda/patch_sigmatel.c

@@ -3408,6 +3408,9 @@ static int get_connection_index(struct hda_codec *codec, hda_nid_t mux,
 	hda_nid_t conn[HDA_MAX_NUM_INPUTS];
 	int i, nums;
 
+	if (!(get_wcaps(codec, mux) & AC_WCAP_CONN_LIST))
+		return -1;
+
 	nums = snd_hda_get_connections(codec, mux, conn, ARRAY_SIZE(conn));
 	for (i = 0; i < nums; i++)
 		if (conn[i] == nid)