hwloc.spec: migrated to SPDX license
    
    No functional change.
    
    Note, hwloc license information can be found via these links:
    
    https://www.open-mpi.org/projects/hwloc/license.php
    
    which points to
    
    https://opensource.org/license/bsd-2-clause/
    
    Signed-off-by: Prarit Bhargava <prarit@redhat.com>