Add getmtu and setmtu interface commands

Bug: 9372485

Change-Id: I0dfa6b1f973426d67f976a9c79be8de90e3d9c19
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
diff --git a/ResponseCode.h b/ResponseCode.h
index 7689ef8..85f183a 100644
--- a/ResponseCode.h
+++ b/ResponseCode.h
@@ -45,6 +45,7 @@
     static const int TetheringStatsResult      = 221;
     static const int DnsProxyQueryResult       = 222;
     static const int ClatdStatusResult         = 223;
+    static const int InterfaceGetMtuResult     = 224;
 
     // 400 series - The command was accepted but the requested action
     // did not take place.