[Kata-hypervisor] kconfig is in for QEMU 4.0!

This should make it easier to take a minimal QEMU configuration and carry it across releases. In particular NEMU probably wants to make --without-default-devices the default and adjust their default-configs/{aarch64,x86_64}-softmmu.mak file. Thanks Yang from Intel and everyone from Red Hat that worked on this. It's nice to see this completed after, ehm, 5.5 years. Paolo