drm/atmel-hlcdc: use helper to get crtc state

DRM core provide helper to access crtc state.
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1458045988-25246-1-git-send-email-a.hajda@samsung.com

drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c

@@ -558,7 +558,7 @@ static int atmel_hlcdc_plane_atomic_check(struct drm_plane *p,
 	if (!state->base.crtc || !fb)
 		return 0;
 
-	crtc_state = s->state->crtc_states[drm_crtc_index(s->crtc)];
+	crtc_state = drm_atomic_get_existing_crtc_state(s->state, s->crtc);
 	mode = &crtc_state->adjusted_mode;
 
 	state->src_x = s->src_x;