fix #4296: virtio-net: enable packed queues for qemu 7.1

fix #4296: virtio-net: enable packed queues for qemu 7.1

virtio 1.1 have improve virtio multiqueue performance,
with a new implementation called "packed queues".

https://www.redhat.com/en/blog/packed-virtqueue-how-reduce-overhead-virtio
https://archive.fosdem.org/2018/schedule/event/virtio/attachments/slides/2167/export/events/attachments/virtio/slides/2167/fosdem_virtio1_1.pdf

This patch enable it by default for qemu 7.1

This don't break old guests with old virtio 1.0 drivers,
as virtio device/devices are forward/backward compatible.

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