drm/sti: Use drm_crtc_vblank_*() API

Non-legacy drivers should only use this API to allow per-CRTC data to be
eventually moved into struct drm_crtc.

Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Vincent Abriou <vincent.abriou@st.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Vincent Abriou <vincent.abriou@st.com>

drivers/gpu/drm/sti/sti_gdp.c

@@ -492,7 +492,7 @@ static void sti_gdp_atomic_update(struct drm_plane *drm_plane,
 		/* Register gdp callback */
 		if (sti_vtg_register_client(mixer->id == STI_MIXER_MAIN ?
 				compo->vtg_main : compo->vtg_aux,
-				&gdp->vtg_field_nb, mixer->id)) {
+				&gdp->vtg_field_nb, crtc)) {
 			DRM_ERROR("Cannot register VTG notifier\n");
 			return;
 		}