drivers: staging: wlan-ng: Remove GPL/MPL boilerplate

Remove the license boilerplate as there is already SPDX license
identifier added in b2441318 ("License cleanup: add SPDX GPL-2.0
license identifier to files with no license") which fulfills the same
intention as the boilerplate.

Cc: Dan Carpenter <error27@gmail.com>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20230517090418.1093091-4-bagasdotme@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>