block: switch all files cleared marked as GPLv2 or later to SPDX tags

All these files have some form of the usual GPLv2 or later boilerplate.
Switch them to use SPDX tags instead.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/bfq-wf2q.c

@@ -1,19 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Hierarchical Budget Worst-case Fair Weighted Fair Queueing
  * (B-WF2Q+): hierarchical scheduling algorithm by which the BFQ I/O
  * scheduler schedules generic entities. The latter can represent
  * either single bfq queues (associated with processes) or groups of
  * bfq queues (associated with cgroups).
- *
- *  This program is free software; you can redistribute it and/or
- *  modify it under the terms of the GNU General Public License as
- *  published by the Free Software Foundation; either version 2 of the
- *  License, or (at your option) any later version.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- *  General Public License for more details.
  */
 #include "bfq-iosched.h"