drm/imx-dc: Switch to drm_atomic_get_new_crtc_state()

The imx-dc 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: Ville Syrjälä <[e-mail]>
Reviewed-by: Liu Ying <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Maxime Ripard <[e-mail]>

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

···
 	}
 
 	crtc_state =
-		drm_atomic_get_existing_crtc_state(state, plane_state->crtc);
+		drm_atomic_get_new_crtc_state(state, plane_state->crtc);
 	if (WARN_ON(!crtc_state))
 		return -EINVAL;