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

Correct Sphinx style comments in include/dm/devres.h
and add the driver model device resource API, devres_*(),
to the HTML documentation.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/api/dm.rst b/doc/api/dm.rst
index 7a77a91..0342620 100644
--- a/doc/api/dm.rst
+++ b/doc/api/dm.rst
@@ -15,3 +15,4 @@
 ------
 
 .. kernel-doc:: include/dm/device.h
+.. kernel-doc:: include/dm/devres.h