drm/atomic: Don't open-code CRTC state destroy

One failure path in crtc_helper had an open-coded CRTC state destroy
which didn't actually call through to the driver's specified state
destroy. Fix that.
Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_crtc_helper.c

@@ -959,7 +959,12 @@ int drm_helper_crtc_mode_set(struct drm_crtc *crtc, struct drm_display_mode *mod
 	if (crtc_funcs->atomic_check) {
 		ret = crtc_funcs->atomic_check(crtc, crtc_state);
 		if (ret) {
-			kfree(crtc_state);
+			if (crtc->funcs->atomic_destroy_state) {
+				crtc->funcs->atomic_destroy_state(crtc,
+				                                  crtc_state);
+			} else {
+				kfree(crtc_state);
+			}
 
 			return ret;
 		}