drm/panel: Constify device node argument to of_drm_find_panel()

The argument is never modified by the function, make it const.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/drm_panel.c

@@ -137,7 +137,7 @@ EXPORT_SYMBOL(drm_panel_detach);
  * Return: A pointer to the panel registered for the specified device tree
  * node or NULL if no panel matching the device tree node can be found.
  */
-struct drm_panel *of_drm_find_panel(struct device_node *np)
+struct drm_panel *of_drm_find_panel(const struct device_node *np)
 {
 	struct drm_panel *panel;
 

include/drm/drm_panel.h

@@ -193,9 +193,9 @@ int drm_panel_attach(struct drm_panel *panel, struct drm_connector *connector);
 int drm_panel_detach(struct drm_panel *panel);
 
 #ifdef CONFIG_OF
-struct drm_panel *of_drm_find_panel(struct device_node *np);
+struct drm_panel *of_drm_find_panel(const struct device_node *np);
 #else
-static inline struct drm_panel *of_drm_find_panel(struct device_node *np)
+static inline struct drm_panel *of_drm_find_panel(const struct device_node *np)
 {
 	return NULL;
 }