rtl8187: fix use after free on failure path in rtl8187_probe()

If allocation of io_dmabuf fails, rtl8187_probe() calls usb_put_dev(udev)
while usb_get_dev(udev) is not called yet. As a result refcnt is decremented
incorrectly and usb_dev can be used after memory deallocation.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtl818x/rtl8187/dev.c

@@ -1636,10 +1636,10 @@ static int rtl8187_probe(struct usb_interface *intf,
 
  err_free_dmabuf:
 	kfree(priv->io_dmabuf);
- err_free_dev:
-	ieee80211_free_hw(dev);
 	usb_set_intfdata(intf, NULL);
 	usb_put_dev(udev);
+ err_free_dev:
+	ieee80211_free_hw(dev);
 	return err;
 }