net: add missing SPDX-License-Identifier for files originating from LiMon

The header of LiMon imported files reference a License file which
does not exist in U-Boot. Some files were forgotten when adding the
SPDX-License-Identifier.
The LiMon files were originally licensed under GPLv2 as can be seen in
commit [2ea91039].

Based on this commit, add the correct SPDX license identifier.
While at it drop the reference to the non-existing License file from all
LiMon files and update the SPDX-License-Identifier to SPDX version 3.

Signed-off-by: Max Merchel <Max.Merchel@ew.tq-group.com>

include/net-legacy.h

@@ -1,9 +1,8 @@
-/* SPDX-License-Identifier: GPL-2.0 */
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  *	LiMon Monitor (LiMon) - Network.
  *
  *	Copyright 1994 - 2000 Neil Russell.
- *	(See License)
  *
  * History
  *	9/16/00	  bor  adapted to TQM823L/STK8xxL board, RARP/TFTP boot added

include/net/tftp.h

@@ -1,10 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  *	LiMon - BOOTP/TFTP.
  *
  *	Copyright 1994, 1995, 2000 Neil Russell.
  *	Copyright 2011 Comelit Group SpA
  *	               Luca Ceresoli <luca.ceresoli@comelit.it>
- *	(See License)
  */
 
 #ifndef __TFTP_H__

net/arp.c

@@ -1,9 +1,8 @@
-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *	Copied from Linux Monitor (LiMon) - Networking.
  *
  *	Copyright 1994 - 2000 Neil Russell.
- *	(See License)
  *	Copyright 2000 Roland Borde
  *	Copyright 2000 Paolo Scaffardi
  *	Copyright 2000-2002 Wolfgang Denk, wd@denx.de

net/arp.h

@@ -1,9 +1,8 @@
-/* SPDX-License-Identifier: GPL-2.0 */
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  *	Copied from Linux Monitor (LiMon) - Networking.
  *
  *	Copyright 1994 - 2000 Neil Russell.
- *	(See License)
  *	Copyright 2000 Roland Borde
  *	Copyright 2000 Paolo Scaffardi
  *	Copyright 2000-2002 Wolfgang Denk, wd@denx.de

net/bootp.c

@@ -1,8 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  *	Based on LiMon - BOOTP.
  *
  *	Copyright 1994, 1995, 2000 Neil Russell.
- *	(See License)
  *	Copyright 2000 Roland Borde
  *	Copyright 2000 Paolo Scaffardi
  *	Copyright 2000-2004 Wolfgang Denk, wd@denx.de

net/bootp.h

@@ -1,8 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  *	Copied from LiMon - BOOTP.
  *
  *	Copyright 1994, 1995, 2000 Neil Russell.
- *	(See License)
  *	Copyright 2000 Paolo Scaffardi
  */
 

net/cdp.c

@@ -1,9 +1,8 @@
-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *	Copied from Linux Monitor (LiMon) - Networking.
  *
  *	Copyright 1994 - 2000 Neil Russell.
- *	(See License)
  *	Copyright 2000 Roland Borde
  *	Copyright 2000 Paolo Scaffardi
  *	Copyright 2000-2002 Wolfgang Denk, wd@denx.de

net/cdp.h

@@ -1,9 +1,8 @@
-/* SPDX-License-Identifier: GPL-2.0 */
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  *	Copied from Linux Monitor (LiMon) - Networking.
  *
  *	Copyright 1994 - 2000 Neil Russell.
- *	(See License)
  *	Copyright 2000 Roland Borde
  *	Copyright 2000 Paolo Scaffardi
  *	Copyright 2000-2002 Wolfgang Denk, wd@denx.de

net/net.c

@@ -1,9 +1,8 @@
-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *	Copied from Linux Monitor (LiMon) - Networking.
  *
  *	Copyright 1994 - 2000 Neil Russell.
- *	(See License)
  *	Copyright 2000 Roland Borde
  *	Copyright 2000 Paolo Scaffardi
  *	Copyright 2000-2002 Wolfgang Denk, wd@denx.de

net/net_rand.h

@@ -1,8 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  *	Copied from LiMon - BOOTP.
  *
  *	Copyright 1994, 1995, 2000 Neil Russell.
- *	(See License)
  *	Copyright 2000 Paolo Scaffardi
  */
 

net/ping.c

@@ -1,9 +1,8 @@
-// SPDX-License-Identifier: GPL-2.0
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *	Copied from Linux Monitor (LiMon) - Networking.
  *
  *	Copyright 1994 - 2000 Neil Russell.
- *	(See License)
  *	Copyright 2000 Roland Borde
  *	Copyright 2000 Paolo Scaffardi
  *	Copyright 2000-2002 Wolfgang Denk, wd@denx.de

net/ping.h

@@ -1,9 +1,8 @@
-/* SPDX-License-Identifier: GPL-2.0 */
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  *	Copied from Linux Monitor (LiMon) - Networking.
  *
  *	Copyright 1994 - 2000 Neil Russell.
- *	(See License)
  *	Copyright 2000 Roland Borde
  *	Copyright 2000 Paolo Scaffardi
  *	Copyright 2000-2002 Wolfgang Denk, wd@denx.de