s390: block: add SPDX identifiers to the remaining files

It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.

Update the drivers/s390/block/ files with the correct SPDX license
identifier based on the license text in the file itself.  The SPDX
identifier is a legally binding shorthand, which can be used instead of
the full boiler plate text.

This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.

Cc: Stefan Haberland <sth@linux.vnet.ibm.com>
Cc: Jan Hoeppner <hoeppner@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Author(s)......: Holger Smolinski <Holger.Smolinski@de.ibm.com>
  *		    Horst Hummel <Horst.Hummel@de.ibm.com>

drivers/s390/block/dasd_devmap.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Author(s)......: Holger Smolinski <Holger.Smolinski@de.ibm.com>
  *		    Horst Hummel <Horst.Hummel@de.ibm.com>

drivers/s390/block/dasd_diag.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Author(s)......: Holger Smolinski <Holger.Smolinski@de.ibm.com>
  * Based on.......: linux/drivers/s390/block/mdisk.c

drivers/s390/block/dasd_eckd.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Author(s)......: Holger Smolinski <Holger.Smolinski@de.ibm.com>
  *		    Horst Hummel <Horst.Hummel@de.ibm.com>

drivers/s390/block/dasd_fba.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Author(s)......: Holger Smolinski <Holger.Smolinski@de.ibm.com>
  * Bugreports.to..: <Linux390@de.ibm.com>

drivers/s390/block/dcssblk.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * dcssblk.c -- the S/390 block driver for dcss memory
  *

drivers/s390/block/scm_blk.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Block driver for s390 storage class memory.
  *

drivers/s390/block/xpram.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Xpram.c -- the S/390 expanded memory RAM-disk
  *