Change the License to meet SPDX allowed licenses.
    
    No functional change.
    
    The bluez license information can be found at...
    
    https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/LICENSES/
    
    The LICENSES directory includes a link to...
    
    https://spdx.org/licenses/GPL-2.0.html
    
    in the 'preferred/GPL-2.0' text file.
    
    That is consistent with the following...
    
    https://docs.fedoraproject.org/en-US/legal/allowed-licenses/
    
    Signed-off-by: David Marlin <dmarlin@redhat.com>