drivers: net: fix memory leak in atusb_probe

syzbot reported memory leak in atusb_probe()[1].
The problem was in atusb_alloc_urbs().
Since urb is anchored, we need to release the reference
to correctly free the urb

backtrace:
    [<ffffffff82ba0466>] kmalloc include/linux/slab.h:559 [inline]
    [<ffffffff82ba0466>] usb_alloc_urb+0x66/0xe0 drivers/usb/core/urb.c:74
    [<ffffffff82ad3888>] atusb_alloc_urbs drivers/net/ieee802154/atusb.c:362 [inline][2]
    [<ffffffff82ad3888>] atusb_probe+0x158/0x820 drivers/net/ieee802154/atusb.c:1038 [1]

Reported-by: syzbot+28a246747e0a465127f3@syzkaller.appspotmail.com
Signed-off-by: NPavel Skripkin <paskripkin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ieee802154/atusb.c

@@ -365,6 +365,7 @@ static int atusb_alloc_urbs(struct atusb *atusb, int n)
 			return -ENOMEM;
 		}
 		usb_anchor_urb(urb, &atusb->idle_urbs);
+		usb_free_urb(urb);
 		n--;
 	}
 	return 0;