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

Correct Sphinx style comments in include/dm/fdtaddr.h
and add the devfdt API to the HTML documentation;
these functions are NOT compatible with live tree.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/api/dm.rst b/doc/api/dm.rst
index 5bb66f2..df605da 100644
--- a/doc/api/dm.rst
+++ b/doc/api/dm.rst
@@ -26,3 +26,4 @@
 .. kernel-doc:: include/dm/of_extra.h
 .. kernel-doc:: include/dm/of_access.h
 .. kernel-doc:: include/dm/of_addr.h
+.. kernel-doc:: include/dm/fdtaddr.h