Fix License: tag to better reflect reality
    
    There are multiple problems with the license tag
    
      - A bunch of QEMU code is GPLv2-only, not GPLv2-or-later
      - Fedora licensing guidelines say that if "GPLv2" is
        listed, it is redundant to list "GPLv2+" / "LGPLv2+",
        since those licenses are forced to be equiv to "GPLv2"
        in the combined work
      - QEMU also includes code / files under MIT and CC-BY
        license
    
    Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>