meson: -display dbus and CFI are incompatible

The generated skeletons for DBus call the finalize method of the parent
type using code like

    G_OBJECT_CLASS (qemu_dbus_display1_chardev_skeleton_parent_class)->finalize (object);

However, the finalize method is defined in a shared library that is not
compiled with CFI.  Do not enable anything that uses gdbus-codegen if
--enable-cfi was specified.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>