drm/simple_kms_helper: Add {enable|disable}_vblank callback support

If simple_kms_helper based driver needs to work with vblanks,
then it has to provide drm_driver.{enable|disable}_vblank callbacks,
because drm_simple_kms_helper.drm_crtc_funcs does not provide any.
At the same time drm_driver.{enable|disable}_vblank callbacks
are marked as deprecated and shouldn't be used by new drivers.

Fix this by extending drm_simple_kms_helper.drm_crtc_funcs
to provide the missing callbacks.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1518425574-32671-2-git-send-email-andr2000@gmail.com
diff --git a/include/drm/drm_simple_kms_helper.h b/include/drm/drm_simple_kms_helper.h
index d9e4c3c..c4e32c5 100644
--- a/include/drm/drm_simple_kms_helper.h
+++ b/include/drm/drm_simple_kms_helper.h
@@ -107,6 +107,24 @@ struct drm_simple_display_pipe_funcs {
 	 */
 	void (*cleanup_fb)(struct drm_simple_display_pipe *pipe,
 			   struct drm_plane_state *plane_state);
+
+	/**
+	 * @enable_vblank:
+	 *
+	 * Optional, called by &drm_crtc_funcs.enable_vblank. Please read
+	 * the documentation for the &drm_crtc_funcs.enable_vblank hook for
+	 * more details.
+	 */
+	int (*enable_vblank)(struct drm_simple_display_pipe *pipe);
+
+	/**
+	 * @disable_vblank:
+	 *
+	 * Optional, called by &drm_crtc_funcs.disable_vblank. Please read
+	 * the documentation for the &drm_crtc_funcs.disable_vblank hook for
+	 * more details.
+	 */
+	void (*disable_vblank)(struct drm_simple_display_pipe *pipe);
 };
 
 /**