ALSA: usb-audio: Fix potential memory leaks

When the driver hits -ENOMEM at allocating a URB or a buffer, it
aborts and goes to the error path that releases the all previously
allocated resources.  However, when -ENOMEM hits at the middle of the
sync EP URB allocation loop, the partially allocated URBs might be
left without released, because ep->nurbs is still zero at that point.

Fix it by setting ep->nurbs at first, so that the error handler loops
over the full URB list.

Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220930100151.19461-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/endpoint.c

@@ -1268,6 +1268,7 @@ static int sync_ep_set_params(struct snd_usb_endpoint *ep)
 	if (!ep->syncbuf)
 		return -ENOMEM;
 
+	ep->nurbs = SYNC_URBS;
 	for (i = 0; i < SYNC_URBS; i++) {
 		struct snd_urb_ctx *u = &ep->urb[i];
 		u->index = i;
@@ -1287,8 +1288,6 @@ static int sync_ep_set_params(struct snd_usb_endpoint *ep)
 		u->urb->complete = snd_complete_urb;
 	}
 
-	ep->nurbs = SYNC_URBS;
-
 	return 0;
 
 out_of_memory: