HMP: add sub command table to info

  Now info command takes a table of sub info commands,
and changed do_info() to do_info_help() to do help funtion
only.
 Note that now "info <unknown-topic>" returns error instead
of list of info topics.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 67569ef..0934b9b 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1521,7 +1521,8 @@
         .args_type  = "item:s?",
         .params     = "[subcommand]",
         .help       = "show various information about the system state",
-        .mhandler.cmd = do_info,
+        .mhandler.cmd = do_info_help,
+        .sub_table = info_cmds,
     },
 
 STEXI