Add properties to make use of pca9554 gpio expander.
Signed-off-by: NMarkus Niebel <Markus.Niebel@tqs.de>
Signed-off-by: NSteffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>