uio: add SPDX license tags

For those without any license text present or short reference
to GPL, add SPDX tag.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/uio/uio_cif.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * UIO Hilscher CIF card driver
  *
  * (C) 2007 Hans J. Koch <hjk@hansjkoch.de>
  * Original code (C) 2005 Benedikt Spranger <b.spranger@linutronix.de>
- *
- * Licensed under GPL version 2 only.
- *
  */
 
 #include <linux/device.h>

drivers/uio/uio_fsl_elbc_gpcm.c

+// SPDX-License-Identifier: GPL-2.0
 /* uio_fsl_elbc_gpcm: UIO driver for eLBC/GPCM peripherals
 
    Copyright (C) 2014 Linutronix GmbH

drivers/uio/uio_hv_generic.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * uio_hv_generic - generic UIO driver for VMBus
  *
  * Copyright (c) 2013-2016 Brocade Communications Systems, Inc.
  * Copyright (c) 2016, Microsoft Corporation.
  *
- *
- * This work is licensed under the terms of the GNU GPL, version 2.
- *
  * Since the driver does not declare any device ids, you must allocate
  * id and bind the device to the driver yourself.  For example:
  *

drivers/uio/uio_netx.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * UIO driver for Hilscher NetX based fieldbus cards (cifX, comX).
  * See http://www.hilscher.com for details.
@@ -5,8 +6,6 @@
  * (C) 2007 Hans J. Koch <hjk@hansjkoch.de>
  * (C) 2008 Manuel Traut <manut@linutronix.de>
  *
- * Licensed under GPL version 2 only.
- *
  */
 
 #include <linux/device.h>

drivers/uio/uio_pci_generic.c

+// SPDX-License-Identifier: GPL-2.0
 /* uio_pci_generic - generic UIO driver for PCI 2.3 devices
  *
  * Copyright (C) 2009 Red Hat, Inc.
  * Author: Michael S. Tsirkin <mst@redhat.com>
  *
- * This work is licensed under the terms of the GNU GPL, version 2.
- *
  * Since the driver does not declare any device ids, you must allocate
  * id and bind the device to the driver yourself.  For example:
  *

drivers/uio/uio_sercos3.c

+// SPDX-License-Identifier: GPL-2.0
 /* sercos3: UIO driver for the Automata Sercos III PCI card
 
    Copyright (C) 2008 Linutronix GmbH