Remove todo from example code

Keeping that in the docs is a bit untidy

Change-Id: Ia95246208cee48df1536b4317a8c896ab2c84fc2
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/firmware-design.rst b/docs/firmware-design.rst
index 266de27..9e206dc 100644
--- a/docs/firmware-design.rst
+++ b/docs/firmware-design.rst
@@ -2031,7 +2031,6 @@
 
         /*
          * Index of the parent power domain node.
-         * TODO: Figure out whether to whether using pointer is more efficient.
          */
         unsigned int parent_node;