Documentation: Add flexible-arrays.rst to the documentation tree

Add flexible-arrays.rst to Documentation/core-api. Add kernel-doc
comments to allow referencing.

Signed-off-by: sayli karnik <karniksayli1995@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
index 0d93d80..2b908ac 100644
--- a/Documentation/core-api/index.rst
+++ b/Documentation/core-api/index.rst
@@ -16,6 +16,7 @@
    cpu_hotplug
    local_ops
    workqueue
+   flexible-arrays
 
 Interfaces for kernel debugging
 ===============================