gpio: pca953x: Add support for TI PCA9536

TI PCA9536 is 4-Bit I2C GPIO expander without interrupt support[1].
Add support for the same.

[1] TRM: http://www.ti.com/lit/ds/symlink/pca9536.pdf

Signed-off-by: Vignesh R <vigneshr@ti.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

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

@@ -21,6 +21,7 @@ Required properties:
 	maxim,max7313
 	maxim,max7315
 	ti,pca6107
+	ti,pca9536
 	ti,tca6408
 	ti,tca6416
 	ti,tca6424

drivers/gpio/gpio-pca953x.c

@@ -861,6 +861,7 @@ static const struct of_device_id pca953x_dt_ids[] = {
 	{ .compatible = "maxim,max7315", .data = OF_953X( 8, PCA_INT), },
 
 	{ .compatible = "ti,pca6107", .data = OF_953X( 8, PCA_INT), },
+	{ .compatible = "ti,pca9536", .data = OF_953X( 4, 0), },
 	{ .compatible = "ti,tca6408", .data = OF_953X( 8, PCA_INT), },
 	{ .compatible = "ti,tca6416", .data = OF_953X(16, PCA_INT), },
 	{ .compatible = "ti,tca6424", .data = OF_953X(24, PCA_INT), },