machine: Add machine_register_compat_props() function

Move the compat_props handling to core machine code.

Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
diff --git a/vl.c b/vl.c
index ebdeaa0..356713e 100644
--- a/vl.c
+++ b/vl.c
@@ -4448,13 +4448,8 @@
             exit (i == 1 ? 1 : 0);
     }
 
-    if (machine_class->compat_props) {
-        GlobalProperty *p;
-        for (i = 0; i < machine_class->compat_props->len; i++) {
-            p = g_array_index(machine_class->compat_props, GlobalProperty *, i);
-            qdev_prop_register_global(p);
-        }
-    }
+    machine_register_compat_props(current_machine);
+
     qemu_opts_foreach(qemu_find_opts("global"),
                       global_init_func, NULL, NULL);