gpio: pca953x: Add TI TCA9539 support

The TCA9539 is almost identical to the PCA9555 and software-compatible
with this driver. It exposes 16 general purpose I/O pins in two 8-bit
configurations.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

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

@@ -24,6 +24,7 @@ Required properties:
 	ti,tca6408
 	ti,tca6416
 	ti,tca6424
+	ti,tca9539
 	exar,xra1202
 
 Example:

drivers/gpio/gpio-pca953x.c

@@ -67,6 +67,7 @@ static const struct i2c_device_id pca953x_id[] = {
 	{ "tca6408", 8  | PCA953X_TYPE | PCA_INT, },
 	{ "tca6416", 16 | PCA953X_TYPE | PCA_INT, },
 	{ "tca6424", 24 | PCA953X_TYPE | PCA_INT, },
+	{ "tca9539", 16 | PCA953X_TYPE | PCA_INT, },
 	{ "xra1202", 8  | PCA953X_TYPE },
 	{ }
 };