drm/atomic-helper: Update reference to drm_crtc_force_disable_all()

drm_crtc_force_disable_all() was renamed to
drm_helper_force_disable_all(), but one reference was not updated.

Fixes: c2d88e06bcb9 ("drm: Move the legacy kms disable_all helper to crtc helpers")
Signed-off-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: Sui Jingfeng <[e-mail]>
Signed-off-by: Javier Martinez Canillas <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/b8c9c[e-mail]

drivers/gpu/drm/drm_atomic_helper.c

···
  * that also takes a snapshot of the modeset state to be restored on resume.
  *
  * This is just a convenience wrapper around drm_atomic_helper_disable_all(),
- * and it is the atomic version of drm_crtc_force_disable_all().
+ * and it is the atomic version of drm_helper_force_disable_all().
  */
 void drm_atomic_helper_shutdown(struct drm_device *dev)
 {