virtio_pci_modern: create admin queue of queried size

Don't limit the admin queue size to VIRTIO_AVQ_SGS_MAX and rather rely
on the queried queue size.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Message-Id: <20240716113552.80599-11-jiri@resnulli.us>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>