ALSA: ali5451: Drop unused variable

The variable runtime is never used, and this might be even a source of
NULL-dereference.  Nothing better than killing it.

Spotted by coverity CID 100862.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/ali5451/ali5451.c

@@ -855,7 +855,6 @@ static void snd_ali_disable_spdif_out(struct snd_ali *codec)
 static void snd_ali_update_ptr(struct snd_ali *codec, int channel)
 {
 	struct snd_ali_voice *pvoice;
-	struct snd_pcm_runtime *runtime;
 	struct snd_ali_channel_control *pchregs;
 	unsigned int old, mask;
 #ifdef ALI_DEBUG
@@ -872,7 +871,6 @@ static void snd_ali_update_ptr(struct snd_ali *codec, int channel)
 		return;
 
 	pvoice = &codec->synth.voices[channel];
-	runtime = pvoice->substream->runtime;
 
 	udelay(100);
 	spin_lock(&codec->reg_lock);