ceph: quota: cleanup license mess

Precise and non-ambiguous license information is important. The recently
added quota.c file has a SPDX license identifier, which is nice, but
at the same time it has a contradictionary license boiler plate text.

  SPDX-License-Identifier: GPL-2.0

versus

  * 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.

Oh well.

As the other ceph related files are licensed under the GPL v2 only, it's
assumed that the SPDX id is correct and the boiler plate was randomly
copied into that patch.

Remove the boiler plate as it is wrong and even if correct it is redundant.

Fixes: fb18a575 ("ceph: quota: add initial infrastructure to support cephfs quotas")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Luis Henriques <lhenriques@suse.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: "Yan, Zheng" <zyan@redhat.com>
Cc: Sage Weil <sage@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: ceph-devel@vger.kernel.org
Acked-by: Luis Henriques <lhenriques@suse.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>