ALSA: usb: Remove unused variable

sound/usb/endpoint.c: In function ‘deactivate_urbs’:
sound/usb/endpoint.c:520:16: warning: unused variable ‘flags’ [-Wunused-variable]
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/endpoint.c

@@ -517,7 +517,6 @@ static int wait_clear_urbs(struct snd_usb_endpoint *ep)
  */
 static int deactivate_urbs(struct snd_usb_endpoint *ep, int force, int can_sleep)
 {
-	unsigned long flags;
 	unsigned int i;
 	int async;