Update to upstream qemu command line for CXL CFMWS

[stellarhopper]

I've pushed an update to the qemu command line generation for --cxl which conforms to the latest version from upstream qemu. Specifically this reworks the CFMWS command line to the new -M cxl-fmw.0.* format. Pulling in this update will require at least commit:
30796f556790 ("Merge tag 'for_upstream' of git://git.kernel.org/pub/scm/virt/kvm/mst/qemu into staging") from upstream qemu.