ALSA: gus: remove redundant pointer private_data

Pointer private_data is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable 'private_data' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/isa/gus/gus_reset.c

@@ -292,7 +292,6 @@ void snd_gf1_free_voice(struct snd_gus_card * gus, struct snd_gus_voice *voice)
 {
 	unsigned long flags;
 	void (*private_free)(struct snd_gus_voice *voice);
-	void *private_data;
 
 	if (voice == NULL || !voice->use)
 		return;
@@ -300,7 +299,6 @@ void snd_gf1_free_voice(struct snd_gus_card * gus, struct snd_gus_voice *voice)
 	snd_gf1_clear_voices(gus, voice->number, voice->number);
 	spin_lock_irqsave(&gus->voice_alloc, flags);
 	private_free = voice->private_free;
-	private_data = voice->private_data;
 	voice->private_free = NULL;
 	voice->private_data = NULL;
 	if (voice->pcm)