hw/usb: simplified usb_enabled The argument is not longer used and the implementation uses now QOM instead of QemuOpts. Signed-off-by: Marcel Apfelbaum <marcel@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Alexander Graf <agraf@suse.de>