ALSA: snd-usb-caiaq: initialize card pointer

Fixes the following warning:

  CC [M]  sound/usb/caiaq/device.o
sound/usb/caiaq/device.c: In function ‘snd_probe’:
sound/usb/caiaq/device.c:500:16: warning: ‘card’ may be used
uninitialized in this function [-Wmaybe-uninitialized]
Signed-off-by: NDaniel Mack <zonque@gmail.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/usb/caiaq/device.c

@@ -485,7 +485,7 @@ static int __devinit snd_probe(struct usb_interface *intf,
 		     const struct usb_device_id *id)
 {
 	int ret;
-	struct snd_card *card;
+	struct snd_card *card = NULL;
 	struct usb_device *device = interface_to_usbdev(intf);
 
 	ret = create_card(device, intf, &card);