Re-enable wayland support
    
    Previous commit accidentally disabled all of wayland support, instead of
    just dropping mesa-libwayland-egl subpackage. This now re-enables
    wayland support and reworks the conditionals so that we only drop drop
    mesa-wayland-egl subpackage in F28+, where it is now part of wayland
    source package.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1564210