gpio: dt-bindings: remove ti,tps65086-gpio binding

This binding is no longer correct, the GPIO information can should be
added to the parent node and not into this child node. See
Documentation/devicetree/bindings/mfd/tps65086.txt for the correct usage.
Signed-off-by: NAndrew F. Davis <afd@ti.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/gpio/gpio-tps65086.txt

-* TPS65086 GPO Controller bindings
-
-Required properties:
- - compatible		: Should be "ti,tps65086-gpio".
- - gpio-controller	: Marks the device node as a GPIO Controller.
- - #gpio-cells		: Should be two. The first cell is the pin number
-			    and the second cell is used to specify flags.
-			    See ../gpio/gpio.txt for possible values.
-
-Example:
-
-	gpio4: gpio {
-		compatible = "ti,tps65086-gpio";
-		gpio-controller;
-		#gpio-cells = <2>;
-	};