vduse: Support set_vq_affinity callback

Since virtio-vdpa bus driver already support interrupt
affinity spreading mechanism, let's implement the
set_vq_affinity callback to bring it to vduse device.
After we get the virtqueue's affinity, we can spread
IRQs between CPUs in the affinity mask, in a round-robin
manner, to run the irq callback.

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Message-Id: <20230323053043.35-6-xieyongji@bytedance.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>