qapi: Convert balloon

Note that the command being dropped uses the deprecated MONITOR_CMD_ASYNC
API, but the new command is a regular synchronous command. There shouldn't
be visible differences though, as MONITOR_CMD_ASYNC is internal only.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/qmp-commands.hx b/qmp-commands.hx
index bbf9bfc..7c377f0 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -703,11 +703,7 @@
     {
         .name       = "balloon",
         .args_type  = "value:M",
-        .params     = "target",
-        .help       = "request VM to change its memory allocation (in MB)",
-        .user_print = monitor_user_noop,
-        .mhandler.cmd_async = do_balloon,
-        .flags      = MONITOR_CMD_ASYNC,
+        .mhandler.cmd_new = qmp_marshal_input_balloon,
     },
 
 SQMP