vdpa_sim: cleanup kiovs in vdpasim_free()

vringh_getdesc_iotlb() allocates memory to store the kvec, that
is freed with vringh_kiov_cleanup().

vringh_getdesc_iotlb() is able to reuse a kvec previously allocated,
so in order to avoid to allocate the kvec for each request, we are
not calling vringh_kiov_cleanup() when we finished to handle a
request, but we should call it when we free the entire device.

Acked-by: Jason Wang <[e-mail]>
Signed-off-by: Stefano Garzarella <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Michael S. Tsirkin <[e-mail]>

drivers/vdpa/vdpa_sim/vdpa_sim.c

···
 static void vdpasim_free(struct vdpa_device *vdpa)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
+	int i;
 
 	cancel_work_sync(&vdpasim->work);
+
+	for (i = 0; i < vdpasim->dev_attr.nvqs; i++) {
+		vringh_kiov_cleanup(&vdpasim->vqs[i].out_iov);
+		vringh_kiov_cleanup(&vdpasim->vqs[i].in_iov);
+	}
+
 	put_iova_domain(&vdpasim->iova);
 	iova_cache_put();
 	kvfree(vdpasim->buffer);