ALSA: mixart: don't print an unintialized variable on error

My static checker complains that "resp" could be unitialized on error
when we print its value.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/mixart/mixart_mixer.c

@@ -965,7 +965,7 @@ static int mixart_update_monitoring(struct snd_mixart* chip, int channel)
 	int err;
 	struct mixart_msg request;
 	struct mixart_set_out_audio_level audio_level;
-	u32 resp;
+	u32 resp = 0;
 
 	if(chip->pipe_out_ana.status == PIPE_UNDEFINED)
 		return -EINVAL; /* no pipe defined */