dbus: Use new bus name, object and interface

The new interface is a more typical use of DBus, exposing multiple
methods for the functions that are available on the object. The legacy
interface by comparison exposed only one method whose arguments selected
sub-commands to be executed. The legacy approach is not terribly
discoverable and leads to a lack of clarity in the client code. The
legacy approach also obscured the implementation with its use of `struct
mbox_dbus_msg`. The new interface wraps around the existing helpers and
so also deals with `struct mbox_dbus_msg`, but this can at least be
removed in the future.

Change-Id: I7113ed8fd2324bf3fb049d8d20acb3fd7fba6de3
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/dbus.h b/dbus.h
index df31ca3..a40bfd1 100644
--- a/dbus.h
+++ b/dbus.h
@@ -1,8 +1,8 @@
 /* SPDX-License-Identifier: Apache-2.0 */
 /* Copyright (C) 2018 IBM Corp. */
 
-#ifndef MBOX_DBUS_H
-#define MBOX_DBUS_H
+#ifndef DBUS_H
+#define DBUS_H
 
 #include <stdint.h>
 #include <stddef.h>