dt-bindings: gpio: pca953x: add nxp,pcal9535

The NXP PCAL9535 is an extended variant of the PCA9535.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

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

@@ -19,6 +19,7 @@ Required properties:
 	nxp,pca9698
 	nxp,pcal6416
 	nxp,pcal6524
+	nxp,pcal9535
 	nxp,pcal9555a
 	maxim,max7310
 	maxim,max7312