Drop have_edk2 global
    
    edk2 binary packages are noarch so they can be installed on
    mismatching architectures, e.g. edk2-aarch64 on x86_64.
    
    So the existing conditionals are not only unnecessary, but
    actively harmful, as they result in edk2-ovmf not being
    dragged in automatically when qemu-system-x86-core is
    installed on e.g. ppc64le.
    
    Signed-off-by: Andrea Bolognani <abologna@redhat.com>