drm: make crtc/encoder/connector/plane helper_private a const pointer

They're only used to store const pointers anyway. This helps to keep
Ville and the compiler happy.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

include/drm/drm_crtc.h

@@ -467,7 +467,7 @@ struct drm_crtc {
 	int framedur_ns, linedur_ns, pixeldur_ns;
 
 	/* if you are using the helper */
-	void *helper_private;
+	const void *helper_private;
 
 	struct drm_object_properties properties;
 
@@ -597,7 +597,7 @@ struct drm_encoder {
 	struct drm_crtc *crtc;
 	struct drm_bridge *bridge;
 	const struct drm_encoder_funcs *funcs;
-	void *helper_private;
+	const void *helper_private;
 };
 
 /* should we poll this connector for connects and disconnects */
@@ -701,7 +701,7 @@ struct drm_connector {
 	/* requested DPMS state */
 	int dpms;
 
-	void *helper_private;
+	const void *helper_private;
 
 	/* forced on connector */
 	struct drm_cmdline_mode cmdline_mode;
@@ -864,7 +864,7 @@ struct drm_plane {
 
 	enum drm_plane_type type;
 
-	void *helper_private;
+	const void *helper_private;
 
 	struct drm_plane_state *state;
 };

include/drm/drm_crtc_helper.h

@@ -197,19 +197,19 @@ extern void drm_helper_mode_fill_fb_struct(struct drm_framebuffer *fb,
 static inline void drm_crtc_helper_add(struct drm_crtc *crtc,
 				       const struct drm_crtc_helper_funcs *funcs)
 {
-	crtc->helper_private = (void *)funcs;
+	crtc->helper_private = funcs;
 }
 
 static inline void drm_encoder_helper_add(struct drm_encoder *encoder,
 					  const struct drm_encoder_helper_funcs *funcs)
 {
-	encoder->helper_private = (void *)funcs;
+	encoder->helper_private = funcs;
 }
 
 static inline void drm_connector_helper_add(struct drm_connector *connector,
 					    const struct drm_connector_helper_funcs *funcs)
 {
-	connector->helper_private = (void *)funcs;
+	connector->helper_private = funcs;
 }
 
 extern void drm_helper_resume_force_mode(struct drm_device *dev);

include/drm/drm_plane_helper.h

@@ -76,7 +76,7 @@ struct drm_plane_helper_funcs {
 static inline void drm_plane_helper_add(struct drm_plane *plane,
 					const struct drm_plane_helper_funcs *funcs)
 {
-	plane->helper_private = (void *)funcs;
+	plane->helper_private = funcs;
 }
 
 extern int drm_plane_helper_check_update(struct drm_plane *plane,