kernel: object: rename z_object_init to k_object_init

Do not use z_ for internal API and rename to k_object_init.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/kernel/queue.c b/kernel/queue.c
index 2625b9a..095ea07 100644
--- a/kernel/queue.c
+++ b/kernel/queue.c
@@ -66,7 +66,7 @@
 
 	SYS_PORT_TRACING_OBJ_INIT(k_queue, queue);
 
-	z_object_init(queue);
+	k_object_init(queue);
 }
 
 #ifdef CONFIG_USERSPACE