ALSA: asihpi - Fix uninitialized variable

Initialize prev_ctl properly before reference:
  sound/pci/asihpi/asihpi.c: In function ‘snd_card_asihpi_mixer_new’:
  sound/pci/asihpi/asihpi.c:2568:30: warning: ‘prev_ctl.dst_node_index’ may be used uninitialized in this function
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/asihpi/asihpi.c

@@ -2578,6 +2578,9 @@ static int __devinit snd_card_asihpi_mixer_new(struct snd_card_asihpi *asihpi)
 	if (err)
 		return -err;
 
+	memset(&prev_ctl, 0, sizeof(prev_ctl));
+	prev_ctl.control_type = -1;
+
 	for (idx = 0; idx < 2000; idx++) {
 		err = hpi_mixer_get_control_by_index(
 				ss, asihpi->h_mixer,