[ALSA] Fix compile warning

EMU10K1/EMU10K2 driver
Removed an unused variable to fix a compile warning.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/emu10k1/emu10k1x.c

@@ -848,7 +848,6 @@ static void snd_emu10k1x_pcm_free(snd_pcm_t *pcm)
 static int __devinit snd_emu10k1x_pcm(emu10k1x_t *emu, int device, snd_pcm_t **rpcm)
 {
 	snd_pcm_t *pcm;
-	snd_pcm_substream_t *substream;
 	int err;
 	int capture = 0;