drm/modes: Fix drm_mode_copy() docs

There is no object id in drm_display_mode anymore.
Remove stale comments to the contrary.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220209091928.14766-2-ville.syrjala@linux.intel.comAcked-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/drm_modes.c

@@ -880,7 +880,7 @@ EXPORT_SYMBOL(drm_mode_set_crtcinfo);
  * @dst: mode to overwrite
  * @src: mode to copy
  *
- * Copy an existing mode into another mode, preserving the object id and
+ * Copy an existing mode into another mode, preserving the
  * list head of the destination mode.
  */
 void drm_mode_copy(struct drm_display_mode *dst, const struct drm_display_mode *src)