ALSA: ali5451: remove redundant pointer 'codec'

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

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

sound/pci/ali5451/ali5451.c

@@ -1484,12 +1484,9 @@ static struct snd_pcm_hardware snd_ali_capture =
 static void snd_ali_pcm_free_substream(struct snd_pcm_runtime *runtime)
 {
 	struct snd_ali_voice *pvoice = runtime->private_data;
-	struct snd_ali *codec;
 
-	if (pvoice) {
-		codec = pvoice->codec;
+	if (pvoice)
 		snd_ali_free_voice(pvoice->codec, pvoice);
-	}
 }
 
 static int snd_ali_open(struct snd_pcm_substream *substream, int rec,