[media] media-ioc-g-topology.rst: fix a c domain reference

One reference there is still using :ref:. Fix it, to solve this
warning:
  Documentation/media/uapi/mediactl/media-ioc-g-topology.rst:236: WARNING: undefined label: media-v2-intf-devnode (if the link has no caption the label must precede a section header)
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/media/uapi/mediactl/media-ioc-g-topology.rst

@@ -234,7 +234,7 @@ desired arrays with the media graph elements.
        -  ``devnode``
 
        -  Used only for device node interfaces. See
-	  :ref:`media-v2-intf-devnode` for details..
+	  :c:type:`media_v2_intf_devnode` for details..
 
 
 .. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.7cm}|