Add kernel-64k to BaseOS/AppStream to mirror c10s
    
    For CentOS Stream 10, these packages are already available in AppStream
    (devel) and BaseOS (all the rest). Mirror this in ELN so they become
    available outside the buildroot.
    
    Fixes https://gitlab.com/cki-project/infrastructure/-/issues/345
    
    Signed-off-by: Michael Hofmann <mhofmann@redhat.com>