enable kvm_pv_eoi cpuflag

enable kvm_pv_eoi cpuflag

Paravirtualized End-of-Interrupt Indication (PV-EOI)
Hosts and guests require two VM exits (context switches from a VM to a Hypervisor) for each interrupt:
one to inject the interrupt, and another to signal the end of the interrupt.

With pv_eoi , they can negotiate a paravirtualized end-of-interrupt feature and only require one switch per interrupt.
Number of exits is reduced by half for interrupt-intensive workloads,
such as incoming network traffic with a virtio network device.
This leads to significant reduction in host CPU utilization for such workloads.

Signed-off-by: Alexandre Derumier <aderumier@odiso.com>