ALSA: usb/6fire: Fix potential NULL pointer dereference in comm.c

'rt' was dereferenced before the NULL check.
Moved the code after the check.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/6fire/comm.c

@@ -129,12 +129,13 @@ int __devinit usb6fire_comm_init(struct sfire_chip *chip)
 {
 	struct comm_runtime *rt = kzalloc(sizeof(struct comm_runtime),
 			GFP_KERNEL);
-	struct urb *urb = &rt->receiver;
+	struct urb *urb;
 	int ret;
 
 	if (!rt)
 		return -ENOMEM;
 
+	urb = &rt->receiver;
 	rt->serial = 1;
 	rt->chip = chip;
 	usb_init_urb(urb);