staging: rtl8192u: release memory on error path

In rtl819xU_tx_cmd if usb_submit_urb fails the allocated memories should
be released.
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Link: https://lore.kernel.org/r/20190920014303.31410-1-navid.emamdoost@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/r8192U_core.c

@@ -1211,6 +1211,8 @@ short rtl819xU_tx_cmd(struct net_device *dev, struct sk_buff *skb)
 		return 0;
 
 	DMESGE("Error TX CMD URB, error %d", status);
+	dev_kfree_skb(skb);
+	usb_free_urb(tx_urb);
 	return -1;
 }