gpio: DT bindings, move tca9554 from pcf857x to pca953x

The TCA9554 is similar to the PCA9554. Update the DT binding docs.
Signed-off-by: NAnders Darander <anders@chargestorm.se>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

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

@@ -26,6 +26,7 @@ Required properties:
 	ti,tca6416
 	ti,tca6424
 	ti,tca9539
+	ti,tca9554
 	onsemi,pca9654
 	exar,xra1202
 

Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt

@@ -25,7 +25,6 @@ Required Properties:
     - "nxp,pcf8574": For the NXP PCF8574
     - "nxp,pcf8574a": For the NXP PCF8574A
     - "nxp,pcf8575": For the NXP PCF8575
-    - "ti,tca9554": For the TI TCA9554
 
   - reg: I2C slave address.