hw/arm/bcm283x: Correct the license text

hw/arm/bcm283x: Correct the license text

The license is the 'GNU General Public License v2.0 or later',
not 'and':

  This program is free software; you can redistribute it and/ori
  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.

Fix the license comment.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200312213455.15854-1-philmd@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>