drm/i915: Add crtc state duplication/destruction functions

The atomic helpers need these to prepare a new state object when
starting a new atomic operation.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index b461f90..2dc6d64 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11652,6 +11652,8 @@
 	.set_config = intel_crtc_set_config,
 	.destroy = intel_crtc_destroy,
 	.page_flip = intel_crtc_page_flip,
+	.atomic_duplicate_state = intel_crtc_duplicate_state,
+	.atomic_destroy_state = intel_crtc_destroy_state,
 };
 
 static bool ibx_pch_dpll_get_hw_state(struct drm_i915_private *dev_priv,