ALSA: es1688: remove redundant pointer chip

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

Cleans up clang warning:
warning: variable 'chip' 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/es1688/es1688.c

@@ -260,7 +260,6 @@ static int snd_es968_pnp_detect(struct pnp_card_link *pcard,
 	struct snd_card *card;
 	static unsigned int dev;
 	int error;
-	struct snd_es1688 *chip;
 
 	if (snd_es968_pnp_is_probed)
 		return -EBUSY;
@@ -276,7 +275,6 @@ static int snd_es968_pnp_detect(struct pnp_card_link *pcard,
 			     sizeof(struct snd_es1688), &card);
 	if (error < 0)
 		return error;
-	chip = card->private_data;
 
 	error = snd_card_es968_pnp(card, dev, pcard, pid);
 	if (error < 0) {