this exposes the FLUSHBYASID CPU flag to nested VMs when running on an
AMD CPU. also reverts a made up check that would advertise
FLUSHBYASID as not supported. this enable certain modern hypervisors
such as VMWare ESXi 7 and Workstation 17 to run nested VMs properly
again.
Signed-off-by: Stefan Sterz <s.sterz@proxmox.com>
