doc: add include/dm/of*.h to the HTML documentation

Correct Sphinx style comments in include/dm/ofnode.h
and add the device tree node API to the HTML documentation;
the ofnode functions are compatible with Live tree or with flat
device tree.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/include/dm/of.h b/include/dm/of.h
index 5cb6f44..9c9065b 100644
--- a/include/dm/of.h
+++ b/include/dm/of.h
@@ -58,14 +58,13 @@
  * struct of_phandle_args - structure to hold phandle and arguments
  *
  * This is used when decoding a phandle in a device tree property. Typically
- * these look like this:
+ * these look like this::
  *
- * wibble {
- *    phandle = <5>;
- * };
- *
- * ...
- * some-prop = <&wibble 1 2 3>
+ *   wibble {
+ *     phandle = <5>;
+ *   };
+ *   ...
+ *   some-prop = <&wibble 1 2 3>
  *
  * Here &node is the phandle of the node 'wibble', i.e. 5. There are three
  * arguments: 1, 2, 3.