xsk: clean up SPDX headers

Clean up SPDX-License-Identifier and removing licensing leftovers.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
diff --git a/net/xdp/xdp_umem.h b/net/xdp/xdp_umem.h
index 7e0b2fa..70fe225 100644
--- a/net/xdp/xdp_umem.h
+++ b/net/xdp/xdp_umem.h
@@ -1,15 +1,6 @@
-/* SPDX-License-Identifier: GPL-2.0
- * XDP user-space packet buffer
+/* SPDX-License-Identifier: GPL-2.0 */
+/* XDP user-space packet buffer
  * Copyright(c) 2018 Intel Corporation.
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms and conditions of the GNU General Public License,
- * version 2, as published by the Free Software Foundation.
- *
- * This program is distributed in the hope it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
- * more details.
  */
 
 #ifndef XDP_UMEM_H_