dpif_netdev: Fix nullable memcpy in queue_netdev_flow_put().

The probe functions try to install a flow without any actions.
For some reason, this only triggers an undefined behavior error after
the next patch in this series.

Fixes: 02bb282 ("dpif-netdev: do hw flow offload in a thread")
Acked-by: Eli Britstein <elibr@nvidia.com>
Acked-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

Author: chaudron

lib/dpif-netdev.c

@@ -3084,7 +3084,7 @@ queue_netdev_flow_put(struct dp_netdev_pmd_thread *pmd,
     flow_offload = &item->data->flow;
     flow_offload->match = *match;
     flow_offload->actions = xmalloc(actions_len);
-    memcpy(flow_offload->actions, actions, actions_len);
+    nullable_memcpy(flow_offload->actions, actions, actions_len);
     flow_offload->actions_len = actions_len;
     flow_offload->orig_in_port = flow->orig_in_port;