docs: Update the vhost section

Change-Id: Ic7a144ffda0d0a3e0f6f9bc1a4790ab36fdf002e
Signed-off-by: jdenisco <jdenisco@cisco.com>
diff --git a/docs/usecases/vhost/iperf-vm.xml b/docs/usecases/vhost/iperf-vm.xml
index be354c5..981c80a 100644
--- a/docs/usecases/vhost/iperf-vm.xml
+++ b/docs/usecases/vhost/iperf-vm.xml
@@ -74,6 +74,7 @@
     <interface type='vhostuser'>
       <mac address='52:54:00:4c:47:f2'/>
       <source type='unix' path='/tmp//vm00.sock' mode='server'/>
+      <driver rx_queue_size='1024' tx_queue_size='1024'/>
       <model type='virtio'/>
       <alias name='net1'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>