qapi: Convert system_powerdown

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/hmp.c b/hmp.c
index 24f30bc..34416fc 100644
--- a/hmp.c
+++ b/hmp.c
@@ -109,3 +109,8 @@
 {
     qmp_system_reset(NULL);
 }
+
+void hmp_system_powerdown(Monitor *mon, const QDict *qdict)
+{
+    qmp_system_powerdown(NULL);
+}