dt-bindings: gpio: Convert Unisoc GPIO controller binding to yaml

Convert the Unisoc gpio controller binding to DT schema format.

Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>