virtio_pci: pass vector policy enum to vp_find_one_vq_msix()

Instead of accessing vp_dev->per_vq_vectors, pass vector policy enum
as an argument of vp_find_one_vq_msix() in preparation for another irq
allocation policy.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Message-Id: <20240716113552.80599-5-jiri@resnulli.us>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>