The node pointer passed to the display timing functions is never
modified, make it const.
Signed-off-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: NTomi Valkeinen <tomi.valkeinen@ti.com>