drm: Mark constant arrays of drm_display_mode const

... and fixup some methods to accept the constant argument.

Now that constant module arrays are loaded into read-only memory, using
const appropriately has some benefits beyond warning the programmer
about likely mistakes.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 080a6e3..60edf9b 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -659,7 +659,7 @@
 extern void drm_mode_probed_add(struct drm_connector *connector, struct drm_display_mode *mode);
 extern void drm_mode_remove(struct drm_connector *connector, struct drm_display_mode *mode);
 extern struct drm_display_mode *drm_mode_duplicate(struct drm_device *dev,
-						   struct drm_display_mode *mode);
+						   const struct drm_display_mode *mode);
 extern void drm_mode_debug_printmodeline(struct drm_display_mode *mode);
 extern void drm_mode_config_init(struct drm_device *dev);
 extern void drm_mode_config_reset(struct drm_device *dev);
@@ -685,8 +685,8 @@
 extern void drm_mode_prune_invalid(struct drm_device *dev,
 				   struct list_head *mode_list, bool verbose);
 extern void drm_mode_sort(struct list_head *mode_list);
-extern int drm_mode_hsync(struct drm_display_mode *mode);
-extern int drm_mode_vrefresh(struct drm_display_mode *mode);
+extern int drm_mode_hsync(const struct drm_display_mode *mode);
+extern int drm_mode_vrefresh(const struct drm_display_mode *mode);
 extern void drm_mode_set_crtcinfo(struct drm_display_mode *p,
 				  int adjust_flags);
 extern void drm_mode_connector_list_update(struct drm_connector *connector);