drm: tilcdc: use vblank hooks in struct drm_crtc_funcs

The vblank hooks in struct drm_driver are deprecated and only meant for
legacy drivers.  For modern drivers with DRIVER_MODESET flag, the hooks
in struct drm_crtc_funcs should be used instead.

While at it, the 'return' of .disable_vblank is dropped to fix the
following checkpatch warning.

 WARNING: void function return statements are not generally useful

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Jyri Sarha <jsarha@ti.com>
Acked-by: Jyri Sarha <jsarha@ti.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1486458995-31018-22-git-send-email-shawnguo@kernel.org
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index f80bf93..93505bc 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -695,6 +695,15 @@
 	return 0;
 }
 
+static int tilcdc_crtc_enable_vblank(struct drm_crtc *crtc)
+{
+	return 0;
+}
+
+static void tilcdc_crtc_disable_vblank(struct drm_crtc *crtc)
+{
+}
+
 static const struct drm_crtc_funcs tilcdc_crtc_funcs = {
 	.destroy        = tilcdc_crtc_destroy,
 	.set_config     = drm_atomic_helper_set_config,
@@ -702,6 +711,8 @@
 	.reset		= drm_atomic_helper_crtc_reset,
 	.atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
 	.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
+	.enable_vblank	= tilcdc_crtc_enable_vblank,
+	.disable_vblank	= tilcdc_crtc_disable_vblank,
 };
 
 static const struct drm_crtc_helper_funcs tilcdc_crtc_helper_funcs = {