drm/imx-dcss: Switch to drm_atomic_get_new_crtc_state()

The imx-dcss atomic_check implementation uses the deprecated
drm_atomic_get_existing_crtc_state() helper.

This hook is called as part of the global atomic_check, thus before the
states are swapped. The existing state thus points to the new state, and
we can use drm_atomic_get_new_crtc_state() instead.

Reviewed-by: Laurentiu Palcu <[e-mail]>
Reviewed-by: Ville Syrjälä <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Maxime Ripard <[e-mail]>

drivers/gpu/drm/imx/dcss/dcss-plane.c

···
 	dma_obj = drm_fb_dma_get_gem_obj(fb, 0);
 	WARN_ON(!dma_obj);
 
-	crtc_state = drm_atomic_get_existing_crtc_state(state,
-							new_plane_state->crtc);
+	crtc_state = drm_atomic_get_new_crtc_state(state,
+						   new_plane_state->crtc);
 
 	hdisplay = crtc_state->adjusted_mode.hdisplay;
 	vdisplay = crtc_state->adjusted_mode.vdisplay;