drm/rcar-du: Replace drm_dev_unref with drm_dev_put

This patch unifies the naming of DRM functions for reference counting
of struct drm_device. The resulting code is more aligned with the rest
of the Linux kernel interfaces.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_drv.c

@@ -437,7 +437,7 @@ static int rcar_du_remove(struct platform_device *pdev)
 	drm_kms_helper_poll_fini(ddev);
 	drm_mode_config_cleanup(ddev);
 
-	drm_dev_unref(ddev);
+	drm_dev_put(ddev);
 
 	return 0;
 }