dt-bindings: gpio: wcd934x: Add bindings for gpio

Qualcomm Technologies Inc WCD9340/WCD9341 Audio Codec has integrated
gpio controller to control 5 gpios on the chip. This patch adds
required device tree bindings for it.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20200107130844.20763-2-srinivas.kandagatla@linaro.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>