dt-bindings: gpio: uniphier: Add hogs parsing

Allow parsing GPIO controller children nodes with GPIO hogs to fix the
following warning:

  uniphier-ld11-ref.dtb: gpio@55000000: 'xirq0-hog' does not match any of the regexes: 'pinctrl-[0-9]+'
      From schema: Documentation/devicetree/bindings/gpio/socionext,uniphier-gpio.yaml

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>