critpath.py: clean up arch handling
    
    armhfp is gone from F37 onwards, so deal with that. Drop FAKEARCH
    as the only remaining arch with a 'fake' is armhfp - just handle
    that one case with a conditional we can remove after F36 is EOL.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>