drm/doc: move damage tracking functions to new section

Move drm_damage_helper function reference from the KMS properties
section to the plane abstraction section. This makes the KMS
properties section more readable for user-space developers.
Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Daniel Vetter <daniel@ffwll.ch>
Cc: Pekka Paalanen <ppaalanen@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201216202222.48146-4-contact@emersion.fr

Documentation/gpu/drm-kms.rst

@@ -376,6 +376,15 @@ Plane Composition Functions Reference
 .. kernel-doc:: drivers/gpu/drm/drm_blend.c
    :export:
 
+Plane Damage Tracking Functions Reference
+-----------------------------------------
+
+.. kernel-doc:: drivers/gpu/drm/drm_damage_helper.c
+   :export:
+
+.. kernel-doc:: include/drm/drm_damage_helper.h
+   :internal:
+
 Display Modes Function Reference
 ================================
 
@@ -484,12 +493,6 @@ Damage Tracking Properties
 .. kernel-doc:: drivers/gpu/drm/drm_damage_helper.c
    :doc: overview
 
-.. kernel-doc:: drivers/gpu/drm/drm_damage_helper.c
-   :export:
-
-.. kernel-doc:: include/drm/drm_damage_helper.h
-   :internal:
-
 Color Management Properties
 ---------------------------