monitor: Add host_net_add device argument completion

Also fix the parameters documentation.

Signed-off-by: Hani Benhabiles <hani@linux.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/hmp.h b/hmp.h
index 0c814d0..22ee836 100644
--- a/hmp.h
+++ b/hmp.h
@@ -109,5 +109,6 @@
                                 const char *str);
 void migrate_set_capability_completion(ReadLineState *rs, int nb_args,
                                        const char *str);
+void host_net_add_completion(ReadLineState *rs, int nb_args, const char *str);
 
 #endif