dt-bindings: gpio: pca953x: document the nxp,pcal6416

The NXP PCAL6416 is a variant of the PCA GPIO expander, with 16 GPIOs.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Documentation/devicetree/bindings/gpio/gpio-pca953x.txt

@@ -16,6 +16,7 @@ Required properties:
 	nxp,pca9574
 	nxp,pca9575
 	nxp,pca9698
+	nxp,pcal6416
 	nxp,pcal6524
 	nxp,pcal9555a
 	maxim,max7310