dm: core: fix member name in ofnode_union documentation

Fixes: 4984de2b ("dm: core: Add ofnode to represent device tree nodes")
Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/dm/ofnode.h

@@ -45,7 +45,7 @@ struct resource;
  * the DT.
  *
  * @np: Pointer to device node, used for live tree
- * @flat_ptr: Pointer into flat device tree, used for flat tree. Note that this
+ * @of_offset: Pointer into flat device tree, used for flat tree. Note that this
  *	is not a really a pointer to a node: it is an offset value. See above.
  */
 typedef union ofnode_union {