vfio-ccw: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style in
header file related to S/390 common i/o drivers.
It assigns explicit block comment to the SPDX License
Identifier.

Changes made by using a script provided by Joe Perches here:
https://lkml.org/lkml/2019/2/7/46.

Fixes: 3cd90214 ("vfio: ccw: add tracepoints for interesting error paths")
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
Message-Id: <20191225122054.GA4598@nishad>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

drivers/s390/cio/vfio_ccw_trace.h

-/* SPDX-License-Identifier: GPL-2.0
- * Tracepoints for vfio_ccw driver
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Tracepoints for vfio_ccw driver
  *
  * Copyright IBM Corp. 2018
  *