In current -next of_graph.h fails to build due to it relying on
linux/types.h without explicitly including it:

../include/linux/of_graph.h:43:71: error: unknown type name 'u32'

caused by bfe446e3 (of: Add of_graph_get_port_by_id function).  Add
an explicit inclusion to fix this.
Signed-off-by: NMark Brown <broonie@kernel.org>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: NPhilipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: NRob Herring <robh@kernel.org>