drm/doc: Include drm_of.c helpers

Fixes a dead link I spotted in the struct drm_crtc docs. Comments
themselves are in a surprisingly good state.

v2: Fix subject typo (Sean).

Reviewed-by: Sean Paul <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

Documentation/gpu/drm-kms-helpers.rst

···
 .. kernel-doc:: drivers/gpu/drm/drm_modeset_helper.c
    :export:
 
+OF/DT Helpers
+=============
+
+.. kernel-doc:: drivers/gpu/drm/drm_of.c
+   :doc: overview
+
+.. kernel-doc:: drivers/gpu/drm/drm_of.c
+   :export:
+
 Legacy Plane Helper Reference
 =============================
 

drivers/gpu/drm/drm_of.c

···
 #include <drm/drm_panel.h>
 #include <drm/drm_of.h>
 
+/**
+ * DOC: overview
+ *
+ * A set of helper functions to aid DRM drivers in parsing standard DT
+ * properties.
+ */
+
 static void drm_release_of(struct device *dev, void *data)
 {
 	of_node_put(data);
···
  * drm_of_component_probe - Generic probe function for a component based master
  * @dev: master device containing the OF node
  * @compare_of: compare function used for matching components
- * @master_ops: component master ops to be used
+ * @m_ops: component master ops to be used
  *
  * Parse the platform device OF node and bind all the components associated
  * with the master. Interface ports are added before the encoders in order to