Turn to_of_node() into a macro in order to support both const and
non-const use. Additionally make the fwnode argument to is_of_node() const
as well.
Signed-off-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: NKieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: NRob Herring <robh@kernel.org>