linux-phytec-fsl

gpio: add bindings for TS-4800 gpio controller

Device tree binding documentation for the TS-4800
GPIO controller.

Signed-off-by: Julien Grossholtz <julien.grossholtz@savoirfairelinux.com>
[Point ngpios to gpio.txt]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>