ALSA: 6fire: remove unused variable card

The pointer card is being assigned a value but it is never used.
Remove this redundant variable. Cleans up clang warning:
Value stored to 'card' is never read
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/usb/6fire/chip.c

@@ -174,11 +174,9 @@ static int usb6fire_chip_probe(struct usb_interface *intf,
 static void usb6fire_chip_disconnect(struct usb_interface *intf)
 {
 	struct sfire_chip *chip;
-	struct snd_card *card;
 
 	chip = usb_get_intfdata(intf);
 	if (chip) { /* if !chip, fw upload has been performed */
-		card = chip->card;
 		chip->intf_count--;
 		if (!chip->intf_count) {
 			mutex_lock(&register_mutex);