sun: Add SPDX license tags to Sun network drivers

Add the appropriate SPDX license tags to the Sun network drivers
as outlined in Documentation/process/license-rules.rst.

Signed-off-by: Shannon Nelson <[e-mail]>
Reviewed-by: Zhu Yanjun <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/sun/Kconfig

···
+# SPDX-License-Identifier: GPL-2.0
 #
 # Sun network device configuration
 #

drivers/net/ethernet/sun/cassini.c

···
+// SPDX-License-Identifier: GPL-2.0
 /* cassini.c: Sun Microsystems Cassini(+) ethernet driver.
  *
  * Copyright (C) 2004 Sun Microsystems Inc.

drivers/net/ethernet/sun/cassini.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
 /* $Id: cassini.h,v 1.16 2004/08/17 21:15:16 zaumen Exp $
  * cassini.h: Definitions for Sun Microsystems Cassini(+) ethernet driver.
  *

drivers/net/ethernet/sun/ldmvsw.c

···
+// SPDX-License-Identifier: GPL-2.0
 /* ldmvsw.c: Sun4v LDOM Virtual Switch Driver.
  *
  * Copyright (C) 2016-2017 Oracle. All rights reserved.

drivers/net/ethernet/sun/niu.c

···
+// SPDX-License-Identifier: GPL-2.0
 /* niu.c: Neptune ethernet driver.
  *
  * Copyright (C) 2007, 2008 David S. Miller ([e-mail])

drivers/net/ethernet/sun/sunbmac.c

···
+// SPDX-License-Identifier: GPL-2.0
 /* sunbmac.c: Driver for Sparc BigMAC 100baseT ethernet adapters.
  *
  * Copyright (C) 1997, 1998, 1999, 2003, 2008 David S. Miller ([e-mail])

drivers/net/ethernet/sun/sungem.c

···
+// SPDX-License-Identifier: GPL-2.0
 /* $Id: sungem.c,v 1.44.2.22 2002/03/13 01:18:12 davem Exp $
  * sungem.c: Sun GEM ethernet driver.
  *

drivers/net/ethernet/sun/sunhme.c

···
+// SPDX-License-Identifier: GPL-2.0
 /* sunhme.c: Sparc HME/BigMac 10/100baseT half/full duplex auto switching,
  *           auto carrier detecting ethernet driver.  Also known as the
  *           "Happy Meal Ethernet" found on SunSwift SBUS cards.

drivers/net/ethernet/sun/sunqe.c

···
+// SPDX-License-Identifier: GPL-2.0
 /* sunqe.c: Sparc QuadEthernet 10baseT SBUS card driver.
  *          Once again I am out to prove that every ethernet
  *          controller out there can be most efficiently programmed

drivers/net/ethernet/sun/sunvnet.c

···
+// SPDX-License-Identifier: GPL-2.0
 /* sunvnet.c: Sun LDOM Virtual Network Driver.
  *
  * Copyright (C) 2007, 2008 David S. Miller <[e-mail]>

drivers/net/ethernet/sun/sunvnet_common.c

···
+// SPDX-License-Identifier: GPL-2.0
 /* sunvnet.c: Sun LDOM Virtual Network Driver.
  *
  * Copyright (C) 2007, 2008 David S. Miller <[e-mail]>