qom: Make object_resolve_path_component() path argument const

A usage with a hardcoded partial path such as

  object_resolve_path_component(obj, "foo")

is totally valid but currently leads to a compilation error. Fix this.

Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/qom/object.c b/qom/object.c
index 351b88c..03e6f24 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1017,7 +1017,7 @@
     return newpath;
 }
 
-Object *object_resolve_path_component(Object *parent, gchar *part)
+Object *object_resolve_path_component(Object *parent, const gchar *part)
 {
     ObjectProperty *prop = object_property_find(parent, part, NULL);
     if (prop == NULL) {