dt-bindings: GPIO: Add TPIC2810 binding

Add binding for TPIC2810 GPO device.

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