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: Andrew F. Davis <afd@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>