drm/vc4: Convert to CRTC VBLANK callbacks

VBLANK callbacks in struct drm_driver are deprecated in favor of
their equivalents in struct drm_crtc_funcs. Convert vc4 over.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200123135943.24140-19-tzimmermann@suse.de
diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index f1e7597..1208258 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -1031,6 +1031,7 @@ static const struct drm_crtc_funcs vc4_crtc_funcs = {
 	.gamma_set = drm_atomic_helper_legacy_gamma_set,
 	.enable_vblank = vc4_enable_vblank,
 	.disable_vblank = vc4_disable_vblank,
+	.get_vblank_timestamp = drm_crtc_vblank_helper_get_vblank_timestamp,
 };
 
 static const struct drm_crtc_helper_funcs vc4_crtc_helper_funcs = {