critpath.py: drop armhfp and a related 
    
    F36 is EOL now, we don't generate critpath for it any more, so
    we don't need armhfp in the critpath arches set any more, and
    we don't need the conditional to drop it for F37+. This also
    fixes a crash if you passed arches on the cmdline.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>