Revert "MTU: Setting of MTU on software interface (instead of hardware interface)"

This reverts commit 70083ee74c3141bbefb185525315f1b34497dcaa.

Reverting as this patch is causing following crash:

0: /home/damarion/cisco/vpp3/build-data/../src/vnet/devices/devices.h:131 (vnet_get_device_input_thread_index) assertion `queue_id < vec_len (hw->input_node_thread_index_by_queue)' fails
Aborted

Change-Id: Ie2a365032110b1f67be7a9d832885b9899813d39
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vnet/devices/virtio/vhost-user.c b/src/vnet/devices/virtio/vhost-user.c
index 34b131c..5460f10 100644
--- a/src/vnet/devices/virtio/vhost-user.c
+++ b/src/vnet/devices/virtio/vhost-user.c
@@ -2869,8 +2869,8 @@
   if (error)
     clib_error_report (error);
 
-  vnet_sw_interface_t *si = vnet_get_hw_sw_interface (vnm, vui->hw_if_index);
-  vnet_sw_interface_set_mtu (vnm, si->sw_if_index, 9000);
+  vnet_hw_interface_t *hi = vnet_get_hw_interface (vnm, vui->hw_if_index);
+  hi->max_l3_packet_bytes[VLIB_RX] = hi->max_l3_packet_bytes[VLIB_TX] = 9000;
 }
 
 /*