virtio_pci: Revert "virtio_pci: support the arg sizes of find_vqs()"

This reverts commit cdb44806: the legacy
path is wrong and in fact can not support the proposed API since for a
legacy device we never communicate the vq size to the hypervisor.

Reported-by: Andres Freund <andres@anarazel.de>
Fixes: cdb44806 ("virtio_pci: support the arg sizes of find_vqs()")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20220816053602.173815-5-mst@redhat.com>